They're both doable with sufficient CPU, RAM and a speedy disk.
I've done both on my iMac Pro and it holds up, with a caveat...
The more you nest, the more performance you're going to loose to virt overhead.
So if the intention is to test a deployment script on a virtual ESXi to deploy a nested SDDC, which will later be used with a physical ESXi box (rather than just a big VM or two), for example, that would be okay but it'll be slow. You're doing Fusion > ESXi > ESXi > workload, so 3 levels of nesting...
If you actually want to use the SDDC that you deploy for testing, lab-purposes, you'd want to do that with the top-level virtualization, meaning a bunch of VMs in Fusion (your scenario 1).
So... scenario 1 = great for tesing the end products, vm's running in esxi-vms will be slower than usual, but totally usable for demo purposes (the less GUI the better tho).
Scenario 2 = sufficient for testing a deployment script that will go onto physical devices.
It depends on your goals to determine the right approach tho.