What? I think you dont understand at all how this works. The database of any password manager is an encrypted file. When you open your password manager and type in the master password it opens that file and decrypts its contents for you and only saves them to memory. It doesnt actually decrypt the file on the drive. When you close the application it doesnt need to be encrypted again. This is exatly the same for all password managers, the only difference is that with web based ones the database file sits on bitwardens server instead of on your harddrive. You are just changing the location of the database, nothing else. Keepass also automatically saves a backup version of the database to a location you can specify and even if you dont you still have better redundancy than with bitwarden because the file sits both in your cloud storage and on each of your devices.

only one password to rememebr as the keepass master key is the encryption key.

keepass database is just a file that you sync using dropbox/gdrive/onedrive/nextcloud/seafile/owncloud/etc.