BlueStacks 4 Hyper-V does not finish booting while Hyper-V is enabled
Yes, this is because I have enabled Virtual Machine Platform and it implicitly enables Hyper-V, because Hyper-V is a native hypervisor, as long as it is enabled Windows boots as a virtual machine and can only access the emulated CPU and can't access the physical CPU, the emulated CPU doesn't support VT-x, so as long as Hyper-V is enabled performance of hosted hypervisors will decrease.
And I found out that Windows Defender Device Guard is also enabled and it also implicitly enables Hyper-V.
So I used these commands in elevated cmd to truly disable Hyper-V:
bcdedit.exe /set hypervisorlaunchtype off
dism /online /disable-feature /featurename:VirtualMachinePlatform
reg add HKLM:\System\CurrentControlSet\Control\DeviceGuard /v EnableVirtualizationBasedSecurity /t REG_DWORD /d 0
shutdown /r /t 0

After that I can't open BlueStacks (Hyper-V), so I uninstalled it and installed the version without Hyper-V, which is faster because of VT-x.