Essentially, Floatplane is a fail over for Youtube. It's not there to replace it, it's there to supplement it and be there in case it disappear. That means that it will never be your source to discover someone, but it will be your source to subscribe to someone that you discovered somewhere else. It's closer to Patreon in that regard (though I believe they still have a bit of discoverability, but it's certainly not your source for that).
That means that most of their function will be geared toward creator, and allow them to offer something more to their viewer (but that for sure will require an account and a paid subscription). One of their interesting current feature for example is to allow streaming to multiple platform (Floatplane, Twitch and Youtube) in parallel.