Part of the fun of selfhosting is the challenge of figuring these things out and building your solutions. If you decide to go with the selfhosted bitwarden variant, there are a couple of options:

1. you can directly dump the entire database on a fixed schedule, compress it into a gzip archive, and store it in a separate location on your VPS. These backups take up very little space and can, with the help of a script, be automated very well.
2. you can use one of the plenty existing bitwarden backup containers that are made for this exact purpose and might offer a more comfortable setup.
3. with any of these solutions, you'd probably want to pull these backups from your local storage to some remote storage, to ensure that in case of an accidental and complete server wipe, no data is lost / a recent backup is available. this can be done with solutions like rclone, to copy the files from your server to a remote location, like an FTP server you've rented or any cloudstorage you may have available.

There's probably even more options, but these are the ones I could think of quickly. If you have questions or need help regarding any of these, let me know, and I'll send you additional ressources to read through.