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).
You can click share on a Youtube video on Firefox and you'll get the option to send it to New Pipe. My only gripe with New Pipe is that it breaks some times and it doesn't have Youtube's recommendations.
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.