Balas are peaceful and wont bother other 'sharks'. Balas will normaly get along with clown loaches. As for whether they wille eat neons - yes they will. Being a fish that can potentialy reach 16", it isn't difficult to see why a 1" fish look like a tempting snack...
Might I ask why you are asking about whether balas are aggressive towards other sharks? Even if they aren't, you can't realy keep another shark with them because the shark will be aggressive towards the balas and balas can be rather nervous fish as keeping them in a good-sized school isn't easy and anything less just adds to their insecurity.