I wonder if its possible to create a CDN property in Cloudflare and set its origin to my already existing domain, in order for Cloudflare CDN to only manage this property, e.g. I want to create a property/domain in Cloudflare named CDN.mydomain.com and set its origin to subdomain.mydomain.com, much like an Akamai property, Akamai does not force you to move your DNS management to them
No, but you can let Cloudflare manage DNS for your existing domain. It doesn’t have to proxy your main domain’s traffic, so you can use it as DNS-only while proxying traffic for the subdomain.
If you’re looking for strictly a CDN, there are plenty out there that do this well. I’ve used KeyCDN in the past.