Most quiet, most positional

Some posters have wisely made the point that you can't force a game to be quiet and positional (well, at least as black) -- that is true. However, you're certainly not going to play some sveshnikov sicilian if you want things to be quiet, know what I mean? There are openings out there like the caro kann and french that can at least focus on more solid, long term, maneuvering, sometimes neutralizing type of play better than others. Just understand that if you wish to play solid as black you're going to have to start with allowing your opponent to dictate the play a little bit -- when you don't make many weaknesses -- like in the caro kann -- the pressure isn't too bad, but it's clearly coming from the opponent at the start, so you have to be patient and capitalize on his errors to slowly take the game over.

Moreover, although these openings can focus on more solid moves, at the same time you will probably be facing some dynamic pressure from a good opponent, and to do that you need defense; and for defense you need tactics; as black especially you will need to prepare yourself to defend against some dynamic ideas, because that's what the more aggressive position is naturally capable of.

All in all, those openings are two suggestions, but don't think you can avoid the "problem" of tactics: some games are more tactical than others, but if you can't see simple tactics quick, it'll really drag you down, and that'll mean you can outplay your opponent for 30 moves but still lose to a shallow, simple, but overlooked tactic; your positional play may have given you a strong position, but your fundamental tactical error lost you a piece, which is more important unfortunately. That used to be me; in fact it still is, just to a lesser extent.

Sorry if this is extremely wordy