I got some brake levers and found out that 2 finger could actually mean 3 finger, so I wasn't happy about that. Then it turns out that the index finger trigger of the shifters I got are roughly 28 miles long. I pushed the brake and shifter as far inboard as possible and I still barely have enough room to get my index finger on the grip. Nowhere have I read that this is a factor, but apparently it is.

The reason I got these Acera shifters is cause the indicator window is on top which I thought was neat. Is this something I should have known about? Maybe it doesn't help that the grips I got have a little "horn" on the outside. That takes up maybe 1/2".

What exactly is the question?

is trigger length a factor that changes between shifters? The “horn” thingys on these grips do take up some room and contributes to the trigger intrusion into the grip area, but swapping grips doesn’t make these triggers seem to fit.

I would expect some variation in shift arm length between brands and models, but it isn't something that is used to sell shifters, e.g. "Acme Super Shifters, 10-speed, 21mm shift arm". Get some wider handlebars or look for different brake levers and shifters that will match what you want.
John

In the pic, it may be possible that by pushing the shifter inboard the curve of the handlebar angles the trigger lever toward the grip. Kinda hard to tell.

If you move the grips outboard a few millimeters = Does it fix the issue? There's the solution.

Sorry - cannot answer q's about trigger lengths between other products.
edit: none will be 28 miles long

re-edit: Horns, or bells, or lights, or mirrors or computers that get in the way of comfortable hand positioning and shifting on the bicycle should be moved. There are too many options available in the market to sacrifice comfort and/or handling.

What prevents you from using 2 fingers on a 3 finger lever?

"Should folks that don't have a clue buy stuff nillie willie and attempt to install it because little red indicator arrow is cool?"

2000% too many fingers...

Just that the extra length is annoying. I got used to the length of the originals.
I don’t like to, but I can’t seem to find a store that showcases all the options. Got any shifter insights to share?

Are you saying you have never bought a bike part willie nillie and tried to install it?

i install lots of Deore, Altus and Alivio trigger shifters... never had an issue or complaint...

is there a difference between the lever throw of the 3- ans 2-1 downshifts? older trigger shifters are famous for sticking pawls due to old, hardened grease.....

You could always grind/file down the end of the shift lever till it's suitable. The decrease in leverage may affect the amount of force needed to shift, but probably not by much, and the price point of an Acera 3-speed shifter means replacement is easy if it all goes wrong.

Have you considered chopping off a bit of the trigger? You could smooth it with a file.

Doesn't seem to be a difference. Since you've seen allot of them, do you prefer or dislike any for any particular reason. For the record, the over-bar indication window is a disappointment. They're tilted so far forward that it makes it tough to see. It now makes sense that most windows are under the bar.
I'll see how new grips feel and will consider this. These were $25 take-offs, so it's not like I'm all that attached to them.

Deore, XT, XTR, in the ascending order of great. The XTRs on my DB ascent are incredible... SLX is cool too, but only made for higher gear counts... i shop ebay and Craigs for bargains or gotta-have-its for repairs here.... used, i mostly buy Deore.
and i never look at the indicators.. i just ride.... some models actually allow the indicator to be removed.

Altus 310 series are worlds better on the 3x side.. the 315s have a really quirky throw increase to it that bugs me.
alivio doesn't have that issue.. and deores are always more responsive/easy to used... XTR demand a high price, even the really old ones.
Acera goes back a few years, IIRC. ergonomics got better as the designs advanced.

the indicator windows are at about 40* rotation from the lever plane on the ones i just looked at... the windows point just about straight up on the top side ones..., which, surprisingly, is about right when you do need to take a peek.... i just ride and ignore them..

I'll have to see what I like on this bike. It's a good old bike after some repairs. I put some riser bars on it to feel like the mtn bikes I had decades ago, but as my muscles get back in shape, I may entertain some drop-ish bars. After riding the smooth rail trail, I was amazed at how devastating the air resistance was.

Really, I'm having just as much fun learning about the mechanic-ing side of this bike as riding it. But as hobbies typically go, I make my wish list of epic components, then settle on the cheapest "good enough" stuff... which is probably more than good enough for what I need. No experience here, but I can't imagine how these Acera shifters or Deore LX deraileur could be improved upon... except for the lever length.

Did moving the shifter&brake attachments outboard (or apart) a slight amount help give more room? .... forgetting of the trigger length, which I am guessing has not been trimmed.

Are the bars too short? or the grips too long?

Getting hands right for how you ride is one of the first essentials. Up there with saddle style.

Moving outboard doesn’t help. They’re just right there in the way. A finger can’t fit between the grip and trigger. I’m guessing this design is more of a leisure thing meant to be incredibly “accessible.”

They’re currently as far inboard as possible due to the curve in the bar. From bar end to inside surface of shifter mount ring is 7”. From tip of trigger to inside mount surface is 3.75”. That doesn’t leave much finger room. Looking at pictures of some shifter/break combos, there is almost no trigger protruding out over the grip, so there’s definitely some variation out there.

The way I read the o.p. they have learned to use the 'standard' arrangement of shifter/brake lever, wrong? Kind of like someone who 'learns' to drive with their left foot on the brake and the right foot on the accelerator. I'm not sure why they mention their index finger on the bars. You brake with your index and middle finger (ring) on the brake lever. You also shift with those very same fingers. Length of brake lever and/or shifter paddles is irrelevant because they have the same origin point. The length of shifter paddles seems very constant between models/brands to meb but I've never really noticed. The classic 2 finger lever is an Avid FX5. I have a cargo bike with the Acera shifter/brake lever combo and have zero issues using it. One reason might be that I have the whole works tilted ... IDK 30° down from horizontal. Puts the levers/paddles where you can operate them efficiently and get your fingers away from them as necessary. Also puts the viewing window right at the top of the bar (intentionally?) so you just glance down at it. Or can, if you can actually see things like gear displays, which I cannot.

You can see my setup in OP. Pretty sure the brake/shifter arrangement is correct. I have no problem manipulating the shifter (or brake, but that's not a problem, just annoyance at the length). The problem is grabbing the grip without bumping the shifter. Even with new standard grips (without the horn thing), my pinky is half off the bar. It's not a secure feeling. (Edit: well the outside of my palm is hanging off… not pinky).

I've decided to take a cutting wheel to the shift lever when I get a chance. Next time I'm in the bike shop, I'll take a peek at what the setups look like.

But is it? Seriously, I've got vertigo from trying to orient myself to your setup. It took me about 8 minutes to realize that you have the grips 90° to horizontal. No wonder your palm is hanging off. That flat area of grip is to support your palm and the bar end levers are supposed to point forwards, not straight up! There's that, also your whole brake/shifter setup is too high (by my reference) try pushing the shifter and maybe also brake levers, down a bit and see if that doesn't get things out of your way. Grinding wheels are a bridge too far. Don't alarms and flashing red lights go off in your head when you contemplate irreversible actions like that? Lastly, with your controls pushed to the center of the bar like that, don't you find that you are lacking necessary leverage to properly control your bike? I have all my controls out to the absolute tip of the bars, and shifter/brake levers flush to the ends of the grips which do not have integral bar ends like yours. My way is not the only right way but you might try it. You might like it.

lol I can see how that can be confusing. Here’s a friendlier pic. Everything is how it should be. I was originally trying to get a good pic showing the proportions of the trigger.