You can only use Spritzee
Swirlix is in fact in LC Ubers which means that it is banned in normal LC play.
However Swirlix is the superior attacker if you could use him. Belly Drum + Unburden gives him the same role as it's evolved form, Slurpuff. Spritzee takes much more time to set up, utilizing a mono attacking set.
Spritzee @ Eviolite
Trait: Aroma Veil
EVs: 212 HP / 196 Def / 12 SpA / 76 SpD/ 12 Spe
- Calm Mind
- Moonblast/Draining Kiss