I've set up a few Nextcloud instances in the last 2 years on Digital Ocean VPSs and Raspberry Pis and I ran into so many problems and difficulties which scaled with the quantity and size of files I hosted on it. I took care in setting up everything to a relatively solid standard (memcache etc.), but I found Nextcloud to be so unreliable for syncing particularly with the official Android and Linux clients. Plus, there was the whole botched version 20 upgrade.
I find Nextcloud tries to solve too many problems turning it into a bloated mess even for a moderately experienced user.
For file storage only, I've found Syncthing on a Raspberry Pi at home syncing over Zerotier (for when I'm not at home) to be a much more robust, user-friendly and scalable solution, despite it syncing whole folders only.