At 1st glance I'd play Rxc1 then Qc7 then Rc8 continuing to attack on the queen side as most of white's pieces are stuck in the king side
What's the best move, here?

Your king is loose but not in immediate danger... but White's is!
Play 1. ...Rxc1+!
2. Bxc1 Qc7
threatening Qc2+ which should do some damage. If he defends, bring your remaining rook to the C-file and crash through, adding knights as needed.
In general your position here is full of weaknesses - your white-squared bishop is tied up defending your advanced pawn, and the white diagonals into your camp are wide open. If white plays an immediate Bh3, he'll create a pin. White should also be able to get his queen down those diagonals pretty quickly, at which point you're toast. Meanwhile your f6 pawn is both attacked and pinned, keeping some of your pieces tied to its defense. I can see why you want to kick that white knight, but neither of your proposed moves is very good at that - white can defend that knight with his bishop, so you're not going to kick it with a rook or queen.
The good news is that you've got your knights in the center, your heavy pieces well centralised, and an open c-file. Meanwhile white has one rook trapped in the corner and his queen half-trapped next to it. Strike at his king IMMEDIATELY and crush him with your big guns before he can get his defense organized!
This is a game I played the other day. I'm playing Black, and it's my turn.
I figure I could...
a) Move my rook to C4, attacking White's knight.
b) Move my other rook or queen to E8, again attacking White's knight.
c) Spend the turn retreating my king.
I spent a long time on this turn, and ended up picking option (a), and eventually lost the game.
What would you all say is the most seemingly optimal play on this turn? (Should I have avoided being in a particular situation here?)