Reset/reformat FileVault-protected machine without login password, macOS Catalina
Firmware password is something you need the password or Apple’s willing assistance to bypass.
FileVault and data encryption is trivial to erase by booting to another OS (Internet Recovery is often the easiest other OS) to wipe and reinstall.
Firmware password and hardware failures are the only things that interfere with an erase and install in my experience, once you have reviewed a couple support articles.
Here are the relevant references and definitions:

https://support.apple.com/en-us/HT204455 Firmware
https://support.apple.com/en-us/HT201314 Recovery
https://support.apple.com/en-us/HT208496 Erase