The general idea is a small boot partition to load kernel and most importantly the drivers for the nic, then mount the Nas over iSCSI and finish loading the os
To be honest a 1TB SATA ssd isnt that much, you could have 10 distros @ 100gb each with extra storage mounted on the nas. 100gb is loads for a Linux OS. I think most of the virtual machines I spin up without a GUI use a 20GB disk
You can also boot directly over the network with pxe/netbootin etc but I’m not sure how that works with an add in network card, as it’s usually a feature of the bios itself