what monitor do you use for the Mac mini

You can use most any (USB-C, HDMI, DisplayPort, DVI or VGA) equipped display with a new Mac mini.

see > Connect a display to Mac mini - Apple Support

Personally I have two Samsung displays connected to one of my Mac mini's and two LG displays connected to the other Mac mini. I also have an older Mac mini setup as a media server, that is connected to a Samsung TV.

Using a 32-in LG 4K UltraFine Ergo (32UN880B) display via a Belkin High Speed HDMI 2.1 4K UHD cable. There are newer versions of this display for even less money than I paid, but it is a beautiful display.

All it takes is money. You can use monitors as suggested or even a 5K monitor from LG or the Mac studio monitor. All depends.

I love this display - just wish the stand were more stable.

The ergo arm on my LG 32UN880B is rock sollid and remains exactly where I position it. Once clamped firmly to the edge of the Desk, that mount point does not change over time either.