1. Sometimes - When smaller, cbs often get along well with other tankmates. However, when they mature they get quite aggressive. It's not uncommon to lose shrimp and small fish to a large adult cbs.
2. Both will eat anything. Meaty food, pellets, etc.
3. Cleaner shrimp very rarely act aggressively towards tankmates. Sometimes you get lucky and get one that will "clean" your fish as well. CBS are nice, but can get quite agressive.
Bo