Contact and Screens

[Chess Ref]

Been reading the other thread and had a couple things i need some feedback on.

1. Player A sets a screen behind Player B, I have noticed most of the time
Player B starts turning and stops when they "feel" the other player there. My thinking is that there needs to be contact,along the lines of displacement and not just touching/rubbing. Is my thinking headed in the right direction ?

2. Player A sets screen , Player B running through key, at last second Player
A moves slightly into Player B,usually minimal contact but contact nonetheless. Should I be looking at this minimal contact as a foul or is this need to be let go unless it is substantional ?

Been working on off-ball the last several weeks and these seem to be the two most occurring SITCH.