Hey! Well how many chops you need is really up to the sample, but if its got drums i would suggest chopping each count (each 1/4 note) making a 4 bar loop 16 chops. These can later be edited individually by adjusting the start point of each chop. If for example you feel that in the 2nd bar theres a part that feels rushed > you just go to for example chop 7 and either make it longer or shorter, get it?
By chopping with care and really listenign to the music you can make it real tight, which should be a goal (at least to me)