Normally, both (or more) monitors get connected to the one (main) card.
As for mining use, you would have to ask on one of their forums.
My PC- Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T.