Thanks for the answer!
I asked Hetzner too but i wanted an opinion from Nextcloud since it is the platform i have decided to use, regardless of provider.
Because of performance and administration it will be better to use only Hetzner Storage Share and not an installed Nextcloud at Hetzner with Hetzner Storage Box. Do you need special Nextcloud features Hetzner does not support ins their Managed Nextcloud?
I would always avoid remote storage as primary or external storage if possible.
Speed won’t be as fast. In such cases, you want a much faster connection for the storage backend compared to the single user. Backup storage isn’t designed to be very responsive (and able to handle well many small files), if many other users push their backup at the same time, it can slow down your connection.
i am currently also in the process of setting up a Nextcloud server with the Hetzner Storagebox as storage for the data directory. I read a lot of guides that are outdated but this one Ultimate guide to a performant and secure Nextcloud Server is very recent and worked perfectly for me. it features everything you need to know from choosing the right hardware on hetzner to basic security measures to using the storage box as backend, among other options.