That's the correct method - if your DNS is hosted outside of the cPanel server you'll need to update the IP there as well. No matter where it is hosted, you'll need to allow for a bit of propagation time while the new IP address updates around the world in DNS.
Correct, you can change the domain's IP there, however if your website's DNS is hosted elsewhere such as in CloudFlare, please make sure to change the A records for root domain and www