This may be a silly question but... If I wanted to change or upgrade my chainring on my Truvativ Touro (example below) to something like this SRAM below or similar ones like the FSA ones, could I? The reason I'm asking is because the chainring on the Touro mounts on the back of the arm whereas other arms like the Sugino Messenger (which also has a flat or aero-ish ring) mount their rings on the front. Does this matter as long as the BCD is the same?

https://farm4.staticflickr.com/3723/9...2b1aac1b_z.jpg

https://ecx.images-amazon.com/images/I/41JY1BxJwdL.jpg

As long as they are the same BCD you will be fine.

Just don't be surprised when you receive a wafer thin chainring OP compared to what you have at the moment/ used to seeing.

Wait really?? I thought mine was already pretty flimsy lol. I thought this would be pretty comparable if not thicker...?

Yep. That's a time-trial chainring. It's not cheap either at ~$100.
Let's see road/ time trial rear axle spacing has been 130mm standard since road groups have been 9 speed; we're up to 11 speed now.
How are these additional speeds fit into the same axle space?

With thinner cassette cogs and corresponding 9/10/11 speed specific chains which vary in width in order to maneuver in between those ever thinner cogs. As a result, chainrings which also interact directly with this chain has to be thinner too abit a little less noticeable than casettes considering there's only 2 up front.
Flip side for manufacturers is that this also lessens the weight of their groupset which is a "serious" selling point for weightweenie roadies.

Thanks for the insightful information! I am still a little hesitant mixing multiple speed parts with fixed specific parts. So I know people used thinner chains for 9 to 11 speed, but does that mean I have to change my chain? I'm assuming not because my rear cog will still be the same.

Correct.
With FG/SS you can pretty much mix and match drivetrain part width as long as the largest width is provided for.