The only way Homelander beats Superman is if he has Kryptonite. Neither side would have a fair victory, Homelander would have to cheat or Superman would just win in a landslide.
In season 3 they hyped up that another character trained for months to fight him, and a full out punch from her dents a filing cabinet and they shoot it like we're supposed to be impressed, superman could obliterate the planet with a flick of his finger from what I'm lead to believe
Depends on the writer. You get a superman DC writer, homelander probably gets treated like every other fascist superman beats up. If it's a "the boys" writer, homelander probably uses kryptonite to rip superman in half in a graphic full-page spread or some shit. You're also gonna be dealing with, are we dropping superman into the relatively hopeless universe of the boys, are we dropping homelander into the DC universe, where he'll probably be right st home with like 30 different characters almost exactly like him, will we come up with some portal stuff, what's going on there
So I dunno, depends on the writer. Ke personally I'd prefer if superman won, cause it's more hopeful and less garth ennis-y.