If you use HDMI, you don't tie up a USB-C (front) or Thunderbolt (rear) port on your Mac Mini to drive your display...but you can't use the display's hub ports.
If you use USB-C 'DisplayPort Alt' instead, you give up a USB-C (front) or Thunderbolt port (rear) on your MacMini in order to gain the display hub ports.
Since it's a USB-C display, not a Thunderbolt display, the total bandwidth of the display's video feed and data stream to/from all hub-attached devices will be limited to the USB-C's bandwidth limit. That's not a problem if you have a wireless keyboard and/or mouse dongle, an SD card reader and other fairly low demand things; if you have an external USB-C SSD or two and want to run them full speed, that could be different (and I'd probably hook it directly to the Mac Mini).
Thankfully you don't have to permanently commit. You can hook the USB-C cable up for now, for example, and switch to HDMI later. You may well already have both cables (be sure they're high enough speed) laying around.