Do we still need to terminate the display port with Catalina? Thank you for the hint about getting better resolution options by holding down the Option key in the Display Prefs on the Mac Mini.
The hard drive on our network-only Mac died and it lost all of its settings and I couldn't get it back to nearly as large as it used to be.  I also went ahead and upgraded from Sierra to Catalina in the process.  We only use it for QuickBooks, which allows our CPA and Bookkeeper and my wife and I to log in remotely and we were lost when that HD failed.
My only remaining question is whether we still need to terminate the display port with Catalina, or perhaps they snuck a firmware update in there where the cursor doesn't slow down to a crawl? I bought a couple of those from OWC after failing to create my own and still have one plugged in.  Does it still need it?  I haven't had time to extensively test, but just thought I'd ask since I didn't notice a huge difference with it out.
Thanks again for the sharp minds here (Everett) who knew about this option trick. Saved me tons of eyestrain and annoyance!
You should not need to terminate the video port of your Mac mini as support for a headless machine is natively supported by macOS - Remote into Mac Mini after a reboot.  I say “should” because while it is supposed to be supported, I’ve run into instances where it would simply fail without it - notably VNC.
Bottom line is that you shouldn’t need it.  But, does it hurt to have it?  No.  It’s also sufficiently inexpensive that getting one so you don’t have to worry about any issues makes it quite feasible.