Passwords may be as good as they can. When they are stored in the same password safe the single password of the safe unlocks all of them. A password safe does not provide real security. At most it helps to distribute your passwords over many devices.
do not put backup codes in any password safe. They are only safe on paper and that only if they are read from the screen on a safe system. 2FA means to have a second independent source for the authentication - that is not given anymore if the backup codes are stored on the same system as the password - that is even true if a different password manager is used.
It is an scalability problem. Your brain isn't going to reliable handle 1000 random passwords. Same with 2fa backups. Tho be my guest if you trust more writing them down manually in a notebook, and hope that notebook does not fall in the wrong hands or gets lost.
Password managers encrypt their data file (or at least they should), provided you use a decent password, it should be no problem to store it even in google cloud. If you read the rest of my post, you should pay attention to the "secure computer" part, you can have that one air gapped, without any LAN or WIFI if you want.
You don't seem to trust password managers, perhaps because your password was keylogged when you opened it in your insecure windows computer. But that's not the password manager fault, you had a malware already intercepting everything. You should prevent this in the first place.