Unless you have a very powerful host system running macOS in a VM is painfully slow. On a 2019 MacBook Air with 16GB or RAM running a virtualized macOS is crawling to render the Finder window.
The biggest problem with virtualizing macOS is that it’s built assuming that a half competent GPU is available, meaning that its software rasterizer is dog slow which is a big problem because no VM simulates a GPU that macOS supports. I’ve heard things about getting GPU passthrough working to fix this but I’ve not tried that myself.
Parallels specifically is much better than e.g. Virtualbox in my experience. Still not really pleasant—there's a lot of latency for some reason, unless you directly pass through the mouse as a USB device—but usable enough.
A few months ago I tried a Mojave and a few older versions of macOS in VirtualBox on a 2013 Thinkpad (Hackintosh) and had no problems with booting nor basic things like Finder and other operations with the GUI. I didn't try more graphics-intensive apps, however, but it was actually surprisingly fast and easy to install from an ISO created using the official source download, minus the workaround I needed for EFI booting from APFS. Building an app with Xcode (the reason for doing all this in the first place) also worked decently.
