The jag will take up about 80-90 gallons on her own. It's doable, but it will all depend on her temperament. If she is mean or too territorial, forget it. JD and GT would work together, but be careful with the Texas. It will also depend on the temperament of the Texas as well. Give it a shot. I would recommend raising them all out from 2-4" sizes so they grow up with each other, which could help in keeping aggression at a minimum later on.
There are a few basic rules. Fish either need ample space and territory or you need to over crowd like crazy and over filtrate too. Easier said then done. Try to keep just a few fish is sometimes toxic regardless of the size, aggression is not dispersed well. but sometimes even the meanest of fish end up being chill. In all honesty if you kept a male Texas in a female jag you probably would end up having them pair and end up with some hybrid. The Jd and gt would end up casualties. Most gts and jds are on the low end of aggression scale. Like a fire mouth ect.