My understanding is that "Best Practice" is to use different companies for different services (not to have all of your "eggs in one basket") in case something goes wrong with one company and they take everything down.

This is what I have...

Domain Name Registrar: Dynadot

DNS: Cloudlare

Hosting: Dreamhost

Email: Fastmail

Should everything be under Cloudflare? I think they also do domain name registration and now, soon email. Not sure off the top of my head if they do hosting.