I quite happy with Immersion 600mW (though its big) not sure about other perhaps TBS Unify PRO 800mW is good I heard. I am going to test recently purchased Rush vtx but directly from seller since Banggood sells clones which look like original and even cost as much but are definitely clones according to manufacturer. So far Rush looks as very nicely designed, but I haven't tested it. I also used TS.. standard cheap vtx which worked ok. Be sure to check your antennas before using high power vtx. If you bend antenna and break coax core it might be like without antenna...