Bitdefender VPN vs. Cloudflare

I recently purchase Bitdefender's Premium VPN - which I find out that I did not need on my iPhone as I already use Cloudflare's 1.1.1.1. I am currently using it on my iMac but sometimes it connects, sometimes not. My question is: do I really need Bitdefender Premium VPN vs. just changing my DNS settings in System Preferences to Cloudflare via this article: http://bit.ly/31uUSZd

If I were to change the DNS settings to Cloudflares and discontinue to use Bitdefender, do I need to change both the Ethernet and Wifi settings? https://cl.ly/3428c3e56fef

Can I assume that I should NOT be using both the Bitdefender Premium VPN AND using the Cloudflare DNS settings?

I am not extremely tech savvy with regards to DNS, VPN etc. so if you can help out, please keep your answer as non-tech as possible.