as I will “mount” the domain involved on my VPS (with its own IP address), could you please confirm what are the correct IPs addresses which I have to set in those two fields in the registrar dashboard?
NS from Cloudflare are:
felipe . ns . Cloudflare . com
stella . ns . Cloudflare . com
Do I have to put the IPs of the above mentioned NS from Cloudflare or I have to consider the IP from my VPS to set somewhere?
You should set the assigned Cloudflare nameservers for your domain nameserver at your domain registar.
Are you begin asked to provide the IP addresses for the assigned CF nameservers?
At Cloudflare dashboard → DNS tab, you add new record, etner the VPS hostname which should be configured at your hosting provider as PTR record for example vps.example.com with the IP 188.8.131.52.
Therefore, point that VPS hostname (DNS record) at DNS tab of CF dashboard to your VPS IP address and make sure it’s proxied