Yea, if you leave a discussion open for our imaginations, we'll go everywhere with it. Especially me since admittedly I have a bad short term memory for things I just read. Frequently you'll see in my posts I miss the info given later by the OP or others. However my bloviating does help me with my understanding of things for myself.

Looks like you have everything figured out other wise. What options are there for that bike at 58cm frame if you do find later you need taller? I didn't look at the 60 cm specs, are they too far out for reach and other things?

Have you plugged your body dimensions into a fit calculator that takes all your proportions in mind and compared them to the 58 and 60 cm frame? I'd certainly try to lean toward the smaller frame, because I've found them more "fun" than the bigger size even though I'm comfortable on both.

No worries at all. I appreciate you taking the time to reply, and you've been very helpful with replies to questions I've had in the past.

If I find I need taller than the extra 1cm, I could get some extra mm with different cranks or saddle, but I'll need the next size up for any more than that. The 60cm would be tall enough, but its reach+ is a few cm longer so not ideal for me.

Yep, done that. The top tube (reach+) of the 58 is the sweet spot for me. The 60 is a bit too long. I'd rather go with the smaller frame too, especially since its available now and the 60 may be a 6 month plus wait.

I did a lot of googling between now and my previous posts, and have figured out that going clipless (with the pedals and shoes I have in mind) will require me to raise my seat 5-6mm. With the 58, that'll leave me with 5-6mm to spare.
Not a lot of wiggle room but doable

Unless you are very picky, stems are cheaper than cranks. So a shorter stem might fix the reach on that 60 cm Domane. However looking at the frame reach they list in the geometry, the difference between the 58 cm and 60 cm is only 3 mm.

There is some very slight differences in the seat tube and head tube angles between the two that will increase reach to the bars some also. Frame Stack between the two increases 2.2 cm for the bigger frame. And BB drop decreases by 3 mm.

I have seen some new bikes that the stem length changes with frame size. Don't know if Trek does the same or not. But for sure the stack and reach numbers they give are frame stack and frame reach which doesn't tell you the true picture of your fit which is to the position of your hands on the handlebar.

When I got my new bike this year, they had two lesser models of the same bike in the shop in a 56 and a 58 cm. They let me ride each for 10 miles and would have let me do more if I'd wanted. It really surprised me which bike I picked as just sitting on it and riding around the lot I was in favor of the one I didn't get. However I could have easily fixed what was wrong for me on the 58 cm bike by changing both cranks and stem. On the 56 I just changed cranks.

Good question. With my strap in pedals, I find that I tend to keep my toes pointed downwards a little bit to engage my calves better. This required me to raise my.saddle slightly.