the more you chop up the more you have to work with.
sometimes when im chopping up a bunch of sht there is a sound im like oh im gunna kill this, and end up findng out that some of the other chops just flow better. Dont limit your self
I just chop up the samples even if I want the loop.If I want the loop I chop it into parts so it hits where I want it too or sometimes the snares/kick is always off time.
it all depends. sometimes its easier to work the drums in after to fit the sample afteryou've choped it. or vise versa, lay the drums and then chop the sample and tune it to fit.