Hi,
Really just try and see how far you get as processors behave differently.
With virtual hardware 11 you are limited to 16 vCPUs in your guest OS.
I'm not sure what the limit is for vHW12 (Fusion 8), but I do suggest to start a bit lower and scale up if you need more.
Your guests will be sharing the CPU resources among each other, so it is not like 4 dual CPU nested VMs need 8 vCPUs in your virtual ESXi.
--
Wil