I tried both, Firefox with ublock and Video Background Play Fix extensions (as someone else pointed out too) is great. But I ended up using NewPipe because I feel it's has a better user experience than the mobile version of the YouTube website (playlist management, audio only, downloading, UI) and it's Open Source.

I still use the Firefox option if newpipe has issues fetching the video (which didn't happened to me for a long time).

It's a preference thing, many options are great.