Well, I've already got a Hoopa-U in ORAS because of powersaves, and I gave it the exact set below (ORAS move tutors are great!)
Hoopa-U @ Choice Scarf
Nature: Jolly
EV Spread: 252 Atk / 4 Def / 252 Spe
- Hyperspace Fury
- Zen Headbutt
- Drain Punch
- Fire Punch / Ice Punch / Gunk Shot
I still haven't decided whether or not I should give it fire punch for steel types, ice punch for common dragons, or gunk shot for bulky fairies. Whatever the case may be, it's probably going to be OU because of its great stats (apart from defense) and good typing leaving it weak to only two things, fairy and bug, the latter being quite common in OU to form volt-turn cores, still not an issue if you pair it with a mon that resists both its weaknesses such as heatran.
Now onto Volcanion. This set's a little cliche, something that probably everyone is going to run because it seems to be most logical, however choice scarf sets are also definitely viable, it's sort of another version of Heatran, having a similar stat spread as well as a similar defensive ability.
Volcanion @ Assault Vest
Nature: Modest
EV Spread: 252 HP / 252 SpA / 4 SpD
- Fire Blast/Lava Plume
- Steam Eruption
- Focus Blast/Sludge Wave
- Earth Power
