Just a quick rule i follow when choosing fish. As for the sizes etc of fish If they can fit a fish in their mouth they probably will eat it.
Also if i remember because of you fighting fish, any fish with a fan like style tail will be attacked by it due to the fighters nature. I found that neons tetras go ok with many fish if they have enough room to move and places to hide. I have a koi angelfish thats around 6 inched big now and I have kept tetra neons in the tank with it in the past with no worries.
Hope this helps you out a little
Good luck