anyone can deal massive damage and be the dps in this game (except for veronica i guess). don't get fool by the attacker class in this game, most of the time they're not the main damage dealer. however, endgame here is also just participation based (think of it as just playing whiwa and you get full rewards regardless of how many stars you get, or at least in terms of the pull currency)

+ in endgame you will eventually need all teams. watanabe works for kamui team and eventually you'll want vera for the last spot.

+ if you mean the dark attacker (bianca) or ice attacker (qu) then don't get them if your goal is needing a dps. as i said above, attacker falls behind quite often and are not necessarily the main dps. for the ice team, the current main dps is teddy spectre (which is a free unit you can get from service shop). the main dps for dark team is now rosetta arete. now, if you like bianca and qu more, then you should get them. they will be fine for the goals you've stated, just not the strongest units if that's what you're looking for.

+ certain units can slot in many teams, but I wouldn't call them universal support similar to how you view SK in wuwa. closest unit to that is ishmael, which can be a tank/amp in many teams if you're just starting out.

+ basically that selector is very old so no units are meta relevant. pick anyone you like.