E24 8 characters is absolutely not enough for a database. Bitwarden themselves suggest at least 14 random characters, and suggest 16 or more to be sure. 8 has the potential to be cracked in a matter of hours.
Obviously it depends on where your password is stored, and any other circumstances by which may alter the variables.
Best practices are :
16 + for random character passwords
(https://bitwarden.com/blog/how-long-should-my-password-be/)
6 + words diceware. (https://ssd.eff.org/module/creating-strong-passwords)
Again, it really depends on other factors, but someone asking ‘how long should a password or a passphrase be for a password manager’, and giving no other information, it must assumed to offer at least what most security experts suggest.