Nerite snails will not reproduce and can have pretty shells. It's best to let the tank grow some algae before adding them so they have food, but you can get by earlier if you supplement them with wafers/veggies.
Amano shrimp will not reproduce and are excellent algae eaters. Again, they do best if you add them after there's algae in the tank, but can be supplemented via wafers/veggies.
Adding both the betta and the other inhabitants are fine aggression wise as long as you've gotten the biofilter ready beforehand, otherwise you could go into a mini-cycle and cause aggression. If you go with african dwarf frogs, I highly recommend using frozen food and spot feeding them via a turkey baster or tweezers, as bettas tend to be pigs and will steal the frogs food without spot feeding and possibly distraction.
