Fastmail supports "masked email", a feature for generating random email addresses. This has 1Password integration and can be set-up on your own domain: https://www.fastmail.help/hc/en-us/articles/4406536368911-Ma... Even before this, Fastmail supported subdomain aliasing. Which you could have on any email host that has customizable forwarding. Including Google Suite (although with GS sending emails from such "aliases…
Not if you properly configure DKIM records for it… https://support.google.com/a/answer/177063