In regards to the tetra's and angels and the food chain, the angels can and may eat neon's once they're big enough. Once they've eaten one, look out...
**In theory** you can add an angel to an established tetra tank (with hiding spots) and the tetra's should be fine as they already know the layout of the tank and all the hiding spots. If, however, you add tetra's later to a tank where there is already an angel living, chances are they'll be turned to plant food. Think of it this way: if a big fish lives in a tank and bite-size morsel of a fish is dropped into the tank, the small fish is probably considered a live snack.
I've had 2 larger angels with a dozen tetra's (neon, glo-light, and silver-tip's) for about 6 months now. I added the angels after the tetra's established the tank. I added my killifish (see my avatar) & female betta about 3-4 months ago. In the last 2 weeks, they have all gained a liking for fresh fish. It started 2 weeks ago when I saw something looked wrong with my black angel. Closer examination showed half of a neon hanging out it's mouth. Within 2 hours, between the black angel, the killi, and the female betta, there was no trace of the tetra. I added 2 true siamese flying fox's the same day a few hours earlier, and by noon the next day one was missing as well as a silvertip. My tetra's are vanishing at a rate of one every few days now. I know the black angel likes them. The larger gold angel has never gone near one. My killi has revealed itself to be quite the hunter in recent weeks. In the morning before lights on, the killi can be found hiding in a bush behind a pillar waiting for an innocent snack to swim by (killi's spend most their time roaming the surface for bugs). When it's feeding time and flakes are being fed, the killi ignores the flakes and tries to get the tetra's while they feed. Once the bloodworms are out though, the killi forgets about all other fish.
If it weren't for your dwarf frogs (unsure of these) and assuming you want to keep your tetra's, I suggest looking into a killi. They are spectacular looking fish. Consider the fact that the one I have (avatar) is very plain as far as killie's go....