I think you should create 5 aliases, for different uses
- Primary/personal communication.
- Sensitive accounts (banking, government, healthcare).
- Online shopping and social media.
- Throwaway/temporary sign-ups.
- Professional/work use.
You can try iCloud’s Hide My Email, this function allows you to create unlimited email aliases. And you only need to manage one iCloud account. However, this function is paid.
In my opinion, the most important thing is to enable TOTP or use Passkeys. For the sensitive and important accounts you mentioned, the top priority is to prevent them from being hacked, so these measures are very effective. I even use only one Outlook email address to register for all my accounts, but I enable TOTP and Passkeys on every single one of them, and I have never had any security issues.
You can use these to protect your accounts:
Bitwarden or ProtonPass — Free, and syncs across all devices
Gmail or Outlook — Enable Advanced Protection Program (Google) or Passwordless (Outlook, Microsoft Account)
For personal use, these are enough, and free
And I think you can try Outlook, Microsoft Account support aliases, and you can even control which aliases are allowed to sign in. For example, you can create a random, scrambled alias that only you know, and never use it to register for any other services. That way, this alias won't exist in any external databases. As for your main Outlook email address, simply disable it as a sign-in alias. Even if hackers obtain that email address, they won't be able to log into your account.
This is the principle of least exposure.