I manage a team doing dev work. I have at least three running systems on my main Mac Pro.
My approach is to bring up the beta on its own SSD and during the cycle slowly migrate the apps I find I still want. It's always a clean approach. By this time in the cycle I am pretty much running on Catalina.
The next stage is to migrate the full Mojave partition to a spinner and keep a small installation of it on an SSD. High Sierra's small install is now on a spinner.
As the older installs age the full system installs get pushed off. the cliff.
This is in a Mac Pro with 12 real cores of Xeon @ 3Ghz, 48GB of RAM, 18TB of spinners, 6.5GB of SSD, and a rotating set of spinners for CCC backups. A network server handles TimeMachine.
My MacBook Pro has a similar regimen.