I don’t have experience with the NUC for my own homelab and kubernetes, but the main things I will say with any kubernetes is the RAM. I have 4 servers on VMware (just to get experience there) and then have Rancher (like Openshift) across them (both a management server and then a 3 VM cluster). Every resource is important, but the RAM is what was eaten up before anything else for me. I have Lenovo Tiny m910q (x 4) with 64GB and that allows me a full on cluster and then some with other VMs too.
Sounds like you made a good choice going with a NUC and 64GB ram. You just may find you want to add another or two depending how much you go beyond just experimenting with k8s and using it to host most of your homelab services.