>>20623762NP.
I've still never used M-Mom. Apparently it's great for Maison, though.
I beat Singles just kind of screwing around on my own (I've played OU competitively for a while).
Found that info I linked really valuable for Doubles and Triples, though (I have no experience in non-singles).
For Doubles I used M-Blaziken, Greninja, Rotom-W, and Garchomp. Didn't really have many close calls. Greninja used Mat Block while Blaziken mega'd and tried to get the other two Pokémon into OHKO territory (either Rock Slide on both, or Low Kick / Flare Blitz on a specific one if I could already OHKO one of them with Blaziken or Greninja).
For singles I used a revolving cast of M-Garchomp, Metagross, Ferrothorn, Talonflame and Conkeldurr. No real method to the madness.
For Triples I filled my Doubles core in with some random Singles mons (Talonflame fits in really easily ofc).
Haven't finished Rotation or Multi yet so can't give any help there.