Okay, the mirroring makes sense now. (I was a rock band drummer, ages ago.)
I’m not clear on #1. So the data cable is USB-C on one end and on the other… is it HDMI which in turn connects to an HDMI-DVI converter?
For #2, if I understand right, the data cable is HDMI on one end connected to the mini, and DVI connected to the monitor. That makes more sense to me. But is it possible to get your hands on a USB-C/Thunderbolt to DVI cable? That will make the connection simpler and will take HDMI out of the equation.
I’m thinking of having both monitors, which I now know to be DVI, connected directly to the Thunderbolt connectors of the Mac mini. If you will need an additional Thunderbolt port, a hub should provide additional ports.