Accuracy drops with fatigue and bad timing for passes. For example if you do a floppy play (with passing at 47) you will see that if you time it too early or late that you will get an errant pass. Wait until the shooter pops open and you will still hit them perfectly.
Also LS has alot to do with players passing too far causing the catcher to either catch out of bounds or bobble the catch. Turbo also increases the pass rate, but at the same time its a lower accuracy pass for the most part. RB passing creates a lot of nice animations and seems like its a better pass causing a higher % (for me atleast it seems this way I dunno, probably just me though).
A passing is similar to RB passing. The biggest problem most people have is passing to the wrong guy, note that there is a circle under the player your about to pass too, once you see that and realize it you will start to find that gently pressing the LS will give you alot better control of not only your players but the passing mechanics as well.