Rainbow Six Extraction supports 1-3 players, regardless of what mode you’re playing on. It only really has one mode. There are just a lot of different variables within that mode. There are no adversarial, PvP modes in Rainbow Six Extraction. Whether playing solo, as a duo, or as a squad of three, you are always up against the Parasite menace, and AI always controls them.
Playing solo is a good idea when first starting, as it allows you to learn the various maps, Operators, enemies, and mission types. The difficulty is automatically adjusted according to how many players are playing, so it’s not like playing solo is much more difficult. It’s harder in some ways, in that you’ll only have one Operator with one set of skills and equipment, so you won’t be as adaptable as a squad. But it’s also easier in other ways because you don’t have to worry about coordinating as a team, and it’s easier to maintain stealth. If you want to grind to level up your Operators, then playing solo might be the way to do it, especially early on when most players haven’t yet mastered the squad tactics that Rainbow Six Extraction demands.
While the entire game can be played solo, Rainbow Six Extraction is really designed to be played in co-op, so you’ll need to join up with a partner or squad if you want to get the most from it. Succeeding as a squad requires a pretty high level of cooperation, so you’re better off joining up with some friends rather than letting the matchmaking fix you up with a couple of other random players. The fact is that, while a squad packs more firepower and a wider variety of skills and equipment than a solo Operator, it’s harder to maintain stealth and proceed systematically with a squad. A stealthy, systematic approach is key to every mission type in Rainbow Six Extraction. Still, if you manage to pull it off with a squad, it’s by far the most satisfying way to play the game.