I have mounted several datasets with NFS and SMB using FreeNAS at the same time without any problems. I have mounted those datasets read-only with NFS for Vero4K and writeable with SMB for PC. I did not have any data corruption so far.
Edit: I think it might be a problem in a multi-user environment with many users not knowing each other. If you are the only one using those mounted shares you actually know what you are doing and there should be no problems in mounting a dataset with NFS and SMB at the same time IMHO.
I now managed to connect Vero to my FreeNAS via SMB.
I just had to add the shares manually , otherwise I had a „File Exists“ error.
But when adding manually, I could enter user and password and now it works flawlessly.
I have never had issues with SMB, admittedly with a QNAP NAS, the issue I find with Kodi is the SMB browser is no good, I prefer to add a network location using SMB, this appears as a permanent share location, I then add video locations using the newly created network location.
I have no issue with 4k or any other video over 1Gb SMB share. my NAS runs ext4 filesystem.
This is only if you have read/write on both and even then only in certain circumstances. This is because the file locking mechanism (the ability to lock a file so others cannot modify it at the same time) is not compatible between NFS and SMB servers so theoretically a client on each SMB and NFS can lock the same file at the same time and each think they are the only client that has a lock to that file. This is an important operation in databases and the like. If one of them, SMB or NFS, is read-only, you will not have issues. Additionally you won’t if you don’t use something that relies on file locking like databases do.