Hey kidder, how's it going? Welcome to PC!
I think you'll fit right in here! There's pretty much a section for everything you've listed - ROM Hacking, Challenges, Game Discussion, anything really. I haven't done much ROM hacking though I can tell you that some of the challenges here are pretty tough. Nuzlockes especially, can't tell you how many times I've gotten a game over screen or lost a crucial team member. ;A;
But yeah if you're looking for some good challenges, I'd suggest The Ones That Got Away or the current FNAF style event they've got over in the challenge forum. Feel free to browse around and pick challenges that sound interesting to you though!
And woo, Showdown! What sort of competitive battling do you like? It'd be awesome if you could pop by
the battle server sometime. We do a whole mix of things - chat, battle, host events etc. It's pretty cool! There are plenty of tournaments and clans to get yourself involved in too. But yeah if you have any questions about the server, you're more than welcome to contact either myself or another BSS. :>
Anyway hope you enjoy yourself! Try and stick around yeah? :]