I assume you don’t intend to copy the files but use them from a remote host? As security is a concern I suppose we’re talking about traffic over the public network where (if I’m not mistaken) kerberos with NFS doesn’t provide encryption, only authentication. You obviously can tunnel NFS with SSH or VPN and I’m pretty sure you can create a kerberos ticket which stores credentials locally for longer periods of time and/or read them from a file.
SSH/VPN obviously causes some overhead, but they also provide encryption over the public network. If this is something ran in a LAN I wouldn’t worry too much about encrypting the traffic and in my own network I wouldn’t worry about authentication either too much. Maybe separate the NFS server to it’s own VLAN or firewall it heavily.