Various fish Can work together. Even with Jags. BUT it really depends on the fish being kept. How small they started off. How crowded the tank is. The aggression levels of all in the tank and of course Individual fish personality will be the ruling factor.
There are plenty of people on here and other places that have larger Jags, Festae, Red Devils, Midas, Vieja, and so on that do just fine. Depending also on tank size. Ive got my RTM and my Jag with some of my Festae, RD, Gold Saum and Vieja species and in a couple different tanks together. Some pushing and fighting here and there. Most are now around 3.5 to 5". The most dominate actually right now have been my Blackbelt and some of my other Vieja. Then the RD, Festae and the Jag and RTM have been pretty laid back. Heck my Gold saum has been more assertive then most as well.. Of course any of that can change or it may not. No one can say for sure what will happen. But ive got several larger tanks just for the reason of splitting fish up and grow out to keep an eye on things. I should be able to house all my fish for life and then some. All you can do is try and see what happens.
BUT if I were to say your weak links in your group..... parrotfish, Dempsey,Green terror (Saums can go either way but I think more are more mellow),firemouth, convict.
The Myan much like is close relative Festae can be pretty stout, get bigger and can have quite an attitude.
Just be prepared in case there is a issue. Have a contingency plan. You may need to make choices in what you want to keep. You may need to invest in other set ups as like I have.
