>>14171188In Random Matchup, with its smaller teamsize, offense becomes more critical. Stall only really exists in 6v6 singles. As the format gets faster (becoming doubles or triples, or as team sizes shrink), stall becomes worse and worse purely because offense becomes easier. All it takes is one of your mons to go down to some random crit to break up your defensive core -- now imagine that happening to a 3-mon stall team compared to a 6-mon one.
In a smaller format; turns are valuable. Moves like U-turn, Protect, and Fake-Out become stronger because they save you a turn switching, a turn of taking damage, and a turn of free damage, respectively.
Speed becomes more critical and each turn counts for more, so moves like Tailwind and Rain Dance w/ Swift Swimmers gain value.
Just look for mons that break the Bulk/Speed/Power "pick two" rule, like Dragonite (Extremespeed is a form of speed, after all...!) or Gengar (immunities, especially to sweet types like Fighting and Ground, are a form of bulk) and try to perpetuate an offense that's difficult to wall.
This could mean overwhelming power, like Specs Rain-boosted STAB Hydro Pumps tend to give; or something more technical like a core built around Volt-Turn abuse. Infernape/Rotom-W/Scarf Hydreigon tend to show up as the latter a lot.
Really, just play around and see what works for you; as long as you don't waste turns, you should do fine.
