I think people using Win 10 will find the NUC slow, as Windows is crap especially if you use Office 365 apps locally like Outlook, Excel, OneDrive as they're not well optimised and have all that telemetry background crap.
With multiple Linux VMs on a 7th Gen i3, I have no performance issues with a 256GB SATA SSD and 12 GB of RAM. I can put many more Linux headless VMs or containers on there with no performance issues.
The NUC is a joke for gaming, though for a 24x7 low powered x64 server it's very very hard to beat as second hand in SA they're available for like R3k for my config.
I looked at a Deskmini A300/X300 and while the performance is much better it's also ended up being like 3-5 times the price with all the customs, taxes, etc etc depending on the config.
I'd rather then just get another NUC and have two or get a i5 newer generation. I think the best proper server would be a HP microserver if you want multiple disks, the gen 10 and gen 10 plus are really nice, but again expensive and very rare second hand which is why I ended up with a NUC myself as around 5W idle, it's using almost no power.
I'll move to an ARM setup once the hypervisor offerings are more abundant and mature.