Didn't play CB or safety but had to know the entire defense. For both of your questions I'd first say, it depends on how the coach teaches it. Before breaking down what we did, it would also bear mentioning the variations in the coverage and some of the things that we used to do. We had a standard Robber, Cloud and Sky as our base cover 3 calls. We ran Robber and Sky primarily to defend Pro sets. If the offense shifted to a 4WR with the back out of the backfield and the TE in the slot, we had to get out of Sky and Robber because now you have the possibility of 4 seam routes which sky and robber are not going to cover well. This is where we went to cloud with a corner squatting in the flat or we'd have him play soft, he had to read the backfield and determine whether he was going to squat or play soft. Or we would jump into our Quarters Coverage.
We numbered the WR's. So in the Pro set with the TE lined up right, the Flanker is #1, TE #2, HB #3. From the weak side the Split End was #1 and the HB was #2, FB #3. So given your scenario of the TE motioning to the slot, it doesn't matter which side, he will always be #2.
How our CB's and S played it.
CB Pattern Reads went like this:
1) Key both #1 and #2 as you back pedal.
2) Always stay deep as the deepest WR in your zone.
3) If #1 runs a short or intermediate route, check vertical for #2 (almost expect it)
4) But and this is where Video games make me sick, do not come out of the back pedal unless someone threatens to go vertical. This way if both #1 and #2 run a short route you can break on the ball.
5) If #1 threatens vertical maintain your cushion and run with him. Stay on his outside hip on the post route.
Deep Middle 1/3 Player:
1) Dropping between the CB's and staying as deep as the deepest WR.
2) Key the release of #2, if he goes vertical then you gotta jump on it.
3) If #2 runs short then check split end or flanker for the post.
We never ran a strict zone where guys just say this is my area and whatever happens I don't care I'm going to drop right there. To put it bluntly, if you can't play man then you can't play zone.