Good questions, to begin with, at later levels with better clubs and balls your precision and accuracy will improve, but at the moment . . .
1. Don’t try to understand why a certain club will not work in certain conditions, eg LW out of 40/50 rough 😭 , you only need to ‘ know’ that it will not work, which moves us to . . .
2. The answer to knowing what club will do what out of rough/sand/fescue etc is to first keep rough notes (type and location) whilst playing and secondly, go practice.
3. There are many many tips and charts available within this forum and on YouTube as a good guide and starting point but your confidence is with your own equip and ball and actually doing it yourself and having your own club notes.
e.g. I have found that with my kit out of 60/70 rough nothing will go further, typically, than a full 7i, others may pitch shorter and have more roll but you need to find out which clubs NOT to use and whether you need distance (carry+roll) or just clearance ie carry to get on the fairway.
hope that helps👍