I don’t think it will “break things”. I’m still pretty new to the homelab world, but have plans for some more self-hosted services down the road. I don’t really know what issues it may cause in the future.
Ultimately, I would like my smb share to be accessible from my phone, my wife’s phone, her macbook etc for family cloud storage. Also, I may lean more into using some linux VMs for testing or playing around with. In reality, I may only use it for manually reading and writing to the share from those non-windows devices, not for syncing. I only really want the sync working from my personal PC to my nas as a pseudo-backup, and also cloud access to my files.
The user I created (sync_user) will only be used to access the NAS, either by a sync utility, or via mapped SMB network drive in windows. It would never be used for anything else. That was my thought process and why I created a standalone user for this task.