Theta EX is 99% Tradeable ONLY with Nameless FR (Trying to trade with any other hack turns the pokes into Bad Eggs)
Just remember to create a save state before trading because some moves crash the game (so far Roost, Hurricane, Origin Pulse, Death Blades, Dragon Ascent, Boomburst, Charming Cry, Drain Kiss, Moonblast, Fairy Wind, Night Daze, Play Rough, Round Eyes, Icicle Crash, Horn Leech, Freeze Dry, Forest Curse, Halloween, Ghost Force, Petal Storm, Y echoed Voice, Snarl, Noble Roar, Grassy and Misty Field, Cotton Guard, Belch, Electrify, Spiky Shield, Sacred and Secret Sword, Venom Drench, Flying Press, Dazzle, Flower Guard, Death Wing, Geomancy, Relic Song and Steam Blast from Theta EX crash in Nameless FR) and other moves change into other ( ex. ThetaEX's Heart Swap becomes Psycho Cut in Nameless FR) I'm currently testing which moves crash and which don't.
Bug bite is the same between both games.
Pokemon related, the only oddity I know is that NFR Sawsbuck becomes Theta EX's Therian Tornadus.
Other than this, Pokemon from these two hacks can be traded.