It is time to start a new thread and share my tips, and we can discuss here.
For those who don't have much information, see SpaceInvaderOne's **VIDEO GUIDE** How to Install MacOS Mojave or High Sierra as a VM
There is not much information about hackintosh in VM, so I will not make an installer guide but some important tips which everyone had miss.
If you wanna get quick start(with opencore), I made a github repo to help people.
*** if you like those tips, don't
Ok, here is what I found:
I was thinking the hfs+ driver was not needed as I'm running Catalina on apfs, but to boot recovery you need hfs driver.
1) VBoxHfs.efi (latest developer version compiled by me at the time of writing) is very slow, it took 3 minutes to boot the recovery, and it works only if in opencore there are ProvideCustomSlide=true and EnableSafeModeSlide=true (without these I have memory allocating 0xa00 type 2 error to boot into recovery).
2) Replacing VBoxHfs.efi