TBH, I'm not 100% sure what dependencies Bitwarden has, but assuming that there are instructions on how to install it from scratch on Debian/Ubuntu, then I suggest starting with Core. It's the most minimal of all of our appliances, so is a good starting point if you are unclear on exactly what you need. Extra software - such as a webserver, etc can be installed via apt.

For future reference, I suggest checking what the apps requirements are. If it's unclear or a bit esoteric, then Core is a good start. If it requires Apache, MySQL/MariaDB and PHP, then the chances are our LAMP (Linux Apache, MySQL/MariaDB & PHP) appliance is a good starting point.