When to self-host email/is it as secure as other email?

Just saying, u shouldn’t buy ur domain from cloudflare. If u do, it will be stuck to cloudflare’s authorative dns nameservers and be unable to be changed. If u buy the domain from other places like namecheap, u are of course free to change its nameservers to cloudflare’s, but u can always change back to smth else if u change ur mind. Buying the domain from cloudflare locks u to their nameservers.