Kinda depends The parity has to be larger than your largest drive. but you can have it move data around between fast and slow drives as it is used. It can do pretty cool stuff with a few clicks. It amazes me every day.

Unraid. Mix and match drive sizes. Its magic

for ease of use i would not use a pci coral. usb just is easier. passing the usb through to a dock or vm is easier. i use unraid and it was extra work to get the pcie vs usb coral setup. I have a nuc with a bunch of ssds for this kinda thing too.

Three versions that I know of have it but you’re right it’s not common. https://www.intel.com/content/www/us/en/support/articles/000091705/intel-nuc.html