Ok, one fuse for the bank it is
That's easier on the wallet.
The two wires is because I'm not going to replace the wires from my existing two banks. They seem quite servicable and redoing them is time and money I don't want to expend. So I have two wires now, which are probably 1/0, and I'll hook them up in parallel. The wire gauge I was asking about before was for jumpers between the batteries.