I have two Mac Minis. One 2012, one 2018. The 2012 is a quad-core i7 with 16 GB of RAM, the 2018 is a 6-core i7 with 32 GB of RAM. So neither of these computers is “slow” by any meaningful definition. Both running Catalina.
Plugged the 2012 into the 2018 via Ethernet, assigned them each 192.168.100.x addresses (no router - just a direct connect, and on a different subnet than my wi-fi network), and I’m using that interface for mounting network drives, Plex, Screen Sharing, etc.
It seemed like things were working very well for a month or so, but lately I’m getting lots of random issues with Screen Sharing & Plex.
Lots and lots of timeouts in Plex, although I’m not sure if that’s more due to the Internet connection to Plex’s servers not working as well since people went in to quarantine.
Screen Sharing is SLOW. Jump Desktop is the same. Like I can move the mouse, and I’ll see two pointers for a second or two - where the mouse was, and where it’s going. Same with clicking. Single click, wait a second or so, the item highlights.
This feels like it should be faster over Ethernet.
On the 2012, looking at the Activity Monitor -> Network the “packets in” and “packets out” are between 130 and 200 while I’m having these problems, and the “data received/sec” and "data sent/sec” are a couple dozen kilobytes. And I’m not having a problem accessing the shared drives in Finder. So I don’t think it’s a network issue.
Oh….and I can hook a monitor up to the 2012, hook up a crappy Logitech keyboard/touchpad combo, and it works reasonably well. But I don’t want to use my Logitech - I’d like to do Screen Sharing so I can use my “real” keyboard and my “real” touchpad. 
Any thoughts / advice?
