It's totally not working for me after hours and hours at this today!
I have enabled sharing on both my MBP and iMac. I cannot see the Mac Mini on either device. The only place I find the Mini is in the side bar - LOCATIONS/NETWORK/MAC MINI. When I double click that icon, I get a blank window and it says "not connected."
The only place I can see a normal resolution of my new Mini is by using an HDMI cable to my LCD projector. Everything looks and works great on my wall! I can scroll my mouse and add text like I should.
When I connect the new mini to the LG monitor with the HDMI cable and adaptor, all I get is a very poor resolution screen that goes beyond the edges. If I have to try another SCALED number in System Prefs/Display, I have to disconnect from the monitor and connect to the LCD. It shows many resolutions available, and they are not the same as your screen shot.
Is there ONE magic setting, or is there something I still am not finding? Also, after 5 minutes the LG monitor goes to black (sleep?), and I have to hard reboot the Mini to get back to the low crappy resolution. For a split second the Apple logo shows on the screen in its proper resolution. And then I have to re-enter my Wifi password.