The current name servers can be found under the “DNS” tab in your Cloudflare Dashboard as @shimi mentioned and verified by using this tool https://dnschecker.org/#NS .
If the ones in your Registrar are different than what Cloudflare Dashboard has instructed you to use, things won’t work properly.
If they do match and you still cannot add CNAME or edit other DNS records as mentioned in your previous post,
That was the rationale to start over and have Cloudflare re-scan your records which might be the quickest way (usually less than 30 minutes) to regain full control in the Cloudflare Dashboard.
Most certainly! Both site performance for international customers and security.