I have seen ghost shrimp, glass shrimp and cherry shrimp with bettas and are pretty darn compatible.. Then I have seen the ones who have been made lovely snacks, or have been left torn apart o_O my Madame pestered my snail to death (poor snail....) and poor submissive Rose got her tail split by her. BUT if I had Spartan with fish like platy, he would pester them, but if he were with submissive balloon mollies (like he was briefly) he would be fine.
Depends on the betta o_O
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.