With Proton Unlimited, you also get stuff like per-site aliases using SimpleLogin, Proton VPN, Proton Drive, Proton Calendar and Proton Pass. But if I’m being honest, only the Mail and VPN are truly complete products.
SimpleLogin is fantastic with a custom domain. Game changer for signing up to websites, especially if you use Bitwarden because they integrate seamlessly. I have paid Proton so the premium version is included for free. Not sure how the free version compares.