The navy is my favorite and I want another weapon that is good to dual wield with. I'm trying to figure out what's best to dual wield with a navy.

For more details, take a look through the appropriate section of the Wheeler, Rawson & Co. essentially this answer Ammo is key and therefor two different guns work best imo. I would assume you could buy two of the same gun though. I believe so, I had two cattleman revolvers that I was duel wielding with but one of them was given to me. Also, the listing below is based on players using a male character – although there's plenty of crossover, female characters do have some different clothing and outfit options which replace certain male clothing unlocks. You can buy 2 of any sidearm when you unlock the capability to do so. It should be noted that although these Red Dead Online rank unlocks will make the listed items available, you'll still need to go and purchase them to actually add them to your inventory ready for use, so don't get too excited until you have enough RDO$ in your account.

Rdr online dual wield