I’m running Proxmox on a i7 desktop, no issues with it. I have a couple of window 7 VMs which run ok. I suspect it’s your Windows VM rather than the host giving poor performance.
As Proxmox installs on bare metal you can devote more resources to the VMs.
You might get better performance based on the guest tools perhaps.
However, it’s a pain to migrate VMs (at least from vmware) to Proxmox.
You can easily test it out, just pop in a spare hdd in your NUC and spin up a VM with your application installed.