Don't think you can mine erc20. Pretty sure they ride on the ethereum network. A lot of miners seem to prefer the AMD cards, which makes them really hard to come by at a good price. gtx 1060 (6GB!), gtx 1070, gtx 1080ti are a lot easier to come by. In my own personal experience, I've made more per day mining on NiceHash than I've made mining eth on a pool. 5 1080tis could probably pull $35+ per day on NiceHash. Could buy a rig with 5 1080tis for under $5k so your payback would be about 4-5 months, speculatively. I'm sure others can provide a lot more info regarding this. Good luck!