I presume you mean windows 11. For that 8 is fine.
Don't count on nested virtualization being available. Apple has to change their internal APIs, and there's not much use case for it (but you never know). Plus, I'd expect it would only virtualize ARM code not the x86 emulation layer.
If you can afford the Max, definitely go that route. Lots more graphics cores (mine runs 3 5K monitors plus the internal without skipping a beat).
Note that the old guidance about leaving cores for the host and total allocation doesn't really carry over from intel to arm. During my TP upgrade last week I had 6 VM's running at once, 8-16 GB each, minimum of 4 cores each, and the machine never even turned on the fans. That's on a 64GB max.
