Right, it is possible to run other VMs while Hyper-V is active. But all in software only. There will be no hardware acceleration for the other guests. Which is required to run 64-bit guests. VMware Workstation will tell you about this when you try.
I've made a simple tool to put a really quick one-click GUI over this bcdedit procedure, Hyper-V Switch. You can get it on GitHub:
GitHub - ygoe/HyperVSwitch: Hyper-V Switch – A simple GUI to enable or disable Hyper-V without uninstallation, allowing the use of other virtualisation solutions.
I think I don't miss the window border transparency, it didn't help readability anyway (in fact it mostly made it worse) and it's not so extremely beautiful that I'd want to keep it. But what is still bugging me is that the text colour of the window title bar is always black. No matter how dark...