What Apple documents in the hypervisor framework is what we know about.
I would not suggest buying or using Apple silicon to run Windows x86-64, Linux x86-64, or any other not-AArch64 operating system. It might work within UTM via emulation, but it’s not going to be speedy. Even with a JIT.
If you want or need lots of guests or want or need nested guests akin to IBM VM on z/Architecture or akin to various of the x86-64 VM vendors can offer, use x86-64 hardware with the necessary virtualization support and associated hardware assists.
If you want nested-guest support in some future macOS version, let Apple know: Product Feedback - Apple