This is what we recommend because in addition to breaking the deadlock, it increases the surface area for attack. Both Bitwarden and Ente accounts now have to be compromised to result in an account take over (vs. just Bitwarden).
Alternatively, you could use either Ente or Aegis in offline mode.
You could also use syncthing to automatically sync your Aegis backup folder to another device. I’m pretty sure Aegis backups are encrypted though, so the deadlock issue remains, and your idea to use a memorable password here could still apply.
Use the same email for both, that’s one less thing to remember.
Ideally, two different passwords are the right approach. It helps to have it written down on a piece of paper, until it becomes muscle memory to type.
Practice the scenario of loosing your phone will also help you understand what to do in case it does happen, it’ll make things clear as to what you need to do or remember in such circumstances.
Aside of everything else said here, practice having a pair of USB hard drives with back up both the codes and your Bitwarden database that you update every other month, you should of course encrypt said backup with any of the tools recommended here.
Why should it be plaintext? Original plaintext can be altered with some reversible scheme that you keep in your head. It can have any level of sophistication, as long as you are able to remember it. Starting with simply reversing the characters or doing other permutations and ending with pretty much any algorithm. Sure, the algorithm in use should be easier to recall than some alternative ciphertext.