Texas and green terror go quite well together, they get to the same kind of size and they have a similar temprement. I've kept all kinds of cichlids and I don't see why any of the above fish won't go together.
You want to get them all as juveniles around the same size and let them grow up with eachother so that they are used to eachtoher. Cause if you had one dominant fish like the oscar, and his little chocolate buddy swimming around and decide to add 2 new fish to the tank it can really upset the balance. like if there is too much of a size difference the new guys will be killed or badly attacked.
Luckily for you all the species you like are good mixers. parachromis, amphilophus and vieja (some not all) are aggressive and not the best mixers.
The joy of getting them small is if at some point the compatibility changes you can easily rehome or move some fish to another tank. also hybridization will not be an issue as none of the above fish can interbreed.
Can I add you might want to keep some dithers in there or perhaps a scavenger or two like clown loaches just so that you have some more activity in the tank. as for dithers you want to steer clear of the larger ones like bala sharks and tinfoil barbs. silver dollars would be good
Tank layout:
Oscar - they are an overall kinda guy, they swim everywhere and don't tend to defend a territory unless they are breeding.
Chocolate - they are the same as oscars in behaviour except that they tend to swim in one place for a while just chilling out
Texas - when young they tend to grab a cave as their territory and will spend a lot of time in there and not let others in
green terror - they tend to swim around a lot and despite their name I've never seen one that was a "terror" to its tankmates, obviously they do exist but its uncommon to get a really mean one.
So in terms of layout I would make 2 caves in different zones of the tank, young fish tend to flock into the caves for protection so it means if one fish is being territorial and claims a cave for himself, a scared or weak fish will go and seek out the other shelter you provided. Add some rocks or fake plants around to try and break up the line of site a little so if a chase or confrontation occurs there will be enough of a chance for the fish to seperate from eachother and cool down.
sounds like a good combo to me and I wish you the best of luck!
