Yes, if the domain uses Cloudflare DNS, and 3rd party SSL is installed on the domain, it will provide data encryption from the end-user machine <-> Cloudflare <-> Hosting server.
If the installed certificate is self-signed, we must enable Full encryption mode from Cloudflare.
When an SSL certificate is issued by a publicly trusted certificate authority(like Rapid SSL), we will have to select Full Strick encryption mode from Cloudflare. Full-stick SSL mode provides encryption from end-users to Cloudflare and from Cloudflare to the origin server.