I left a comment a month ago. It has not been addressed.

there's one part that's going to appear very confusing.

I have my (small) laptop. Lets say I want any new (big) screen to appear on the left. So I save "Extend to left".
So I'd expect to see: monitor, laptop.

What will happen, is it will extend my biggest screen to the left, leaving me with:
laptop, monitor

rendering the option seemingly broken.

It's artbitrary depending on what size monitor you happen to plug in.