Be aware that the current 2020 Mac Mini is pretty much the same as the 2018 ones with only a small refresh/speed bump. Some people with the 2018 machines have also had problems with the recent MacOS supplemental update, to the point of having to send in their computers and have them repaired, the logic board replaced.
Aside from that, what benefits do you anticipate from going to the Mac Mini? do you really need a machine that has a bunch of the older "legacy" ports on it, too, or would they just be excess baggage and never used? For a lot of people those legacy ports are very handy if they've still got and need to continue using a lot of peripherals using USB-A, but for those of us who are all-in now with just USB-C and Thunderbolt ports for everything (USB-C or NVME/Thunderbolt 3 external SSDs, for instance), those legacy ports are a waste of space and yet you're paying for them as being included as part of the machine....
You mention using a couple of the LG 4K Thunderbolt 3 24" monitors with the new machine -- I'm not sure that it is possible to plug in two of those to the Thunderbolt 3 ports; I suspect it's not. More likely, you would have to plug in one monitor using a different cable -- HDMI or whatever -- and if that makes a difference to you, best to know that ahead of time, even before making a purchase!
I love my current setup of a 15" 2018 MBP with the 24" LG Thunderbolt 3 4K monitor plugged into it, and that serves as my desktop replacement, while I also have a 12" 2017 MacBook to be my companion on trips away from home....and this works out well for me. A couple of times for various reasons I have unplugged the monitor from the 15" MBP to take it somewhere, and all still works just fine and it's easy and quick enough to plug the monitor back in when I'm ready to do so.
On a regular basis I also plug in a Samsung X5 NVME external SSD to one of the other Thunderbolt 3 ports and that works just great, but I did notice that when I tried to leave the external drive plugged in all the time that there were some issues with everything starting up properly when I booted from a cold start or even just rebooted, so that leads me to come to the conclusion that two very powerful Thunderbolt 3 devices connected to the one computer is enough.