For me, "important" basically means "if somebody somehow stole my 1Password vault and had access its contents, it would be logistically problematic for me that they'd have the MFA for this account". So email, banks, cell phone / DNS hosting / etc, but also things like my MFA for Slack, PyPI, Steam, etc.
Things that aren't important are accounts like my rewards account w/ airlines, various forums / etc where there's MFA but it's less valuable than the password vault itself.
For MFA enrollment, my basic approach is:
1. If the site supports FIDO2/U2F, I enroll a yubikey in that.
2. If it supports multiple FIDO2/U2F devices, I enroll 2 other yubikeys (My primary yubikey is USB-C, then I've got a USB-A and a backup USB-A)
3. If the site supports TOTP, I generate a TOTP key and enroll my phone's TOTP app
4. For sites I'm likely to need to log into a lot, but that don't support multiple FIDO2 devices, I also enroll my Yubikey as a TOTP device ( https://www.yubico.com/products/yubico-authenticator/ for reference). I don't do this for every site because the Yubikey has a finite number of slots for TOTP secrets.
Things that aren't important are accounts like my rewards account w/ airlines, various forums / etc where there's MFA but it's less valuable than the password vault itself.
For MFA enrollment, my basic approach is:
1. If the site supports FIDO2/U2F, I enroll a yubikey in that.
2. If it supports multiple FIDO2/U2F devices, I enroll 2 other yubikeys (My primary yubikey is USB-C, then I've got a USB-A and a backup USB-A)
3. If the site supports TOTP, I generate a TOTP key and enroll my phone's TOTP app
4. For sites I'm likely to need to log into a lot, but that don't support multiple FIDO2 devices, I also enroll my Yubikey as a TOTP device ( https://www.yubico.com/products/yubico-authenticator/ for reference). I don't do this for every site because the Yubikey has a finite number of slots for TOTP secrets.