RE: Pull ups/chins
It doesn't matter.
The common usage seems to be that "chins" are done with an underhand (supinated) grip, while "pull-ups" are done with an overhand (pronated) grip. There is no logic to which one has which name. The movement is the same, but they can be done in lots of different ways. You could also use a neutral grip if you have two parallel bars so you can have your palms facing each other.
An underhand grip involves more biceps, and consequently less lats - apart from that there's no difference.