I'll save you the trouble. Volt White 2 100%
I wouldn't bother with Kaizo White 2 for now because it is such an unbalanced mess. Starters evolve at level 24 and 40 for no reason, Pseudo Legends evolve at level 85, NPCs have pokemon with buffed abilities and moves that you don't have access to, and the Elite 4 is literally impossible without a specific team (especially since Iris's team consist of pokemon that came out of an action replay like sturdy shedinja and wonder guard spiritomb). Currently, the page for the game on this website has been deleted by the user most likely to fix the game to actually be beatable. Also this isn't made by SHF and it's the creator's first ROM hack.
Volt White 2 is a classic that's hard but fair. I would go for that ROM hack. You can't go wrong with a ROM hack made by someone as experienced in ROM hacking as Drayano.
