@Simon_Manning & @RGJ - The Cloudflare write-up has been updated to provide the 3 main options and their trade-offs. Hopefully, this addresses the various issues you raised with the first options presented.
@kelv You might consider placing a footnote in the main description to the CloudFlare write-up. It will save people time that it applies to. Configure direct-delivery incoming email for self-hosted sites with Mail-Receiver - #541 by LotusJeff