I use a Windows 2012 Storage Server virtual machine as storage for my movies and music. I’m using SMB right now, but doing some testing on NFS because Windows 2012 supports NFS 4.1 quite nicely, and it’s not hard to integrate Linux UID/GID into Windows with a Windows domain.
Using Windows is key for me, as all my movie file creation toolchain is Windows, and it’s just easier to store the final product on a share on a domain-joined computer. And, that’s my advice…use the storage system that lets you most easily manipulate the files for the harder things (adding artwork, renaming files, etc.), because playback using OSMC is mostly a read-only task. You only have to create the connection to your NAS once on OSMC/Kodi, while you likely manipulate files a lot using non-OSMC/Kodi methods.
So, if you can set up a Linux-based NAS (either OOB or build-it-yourself) to allow you to manipulate the files the way you want, then that’s probably the best way, as NFS from OSMC is easier (IMHO), even for a one-time setup thing.