Maybe with different servers. But then you need a good aggregation tool and seamless experience shifting between them.

PeerTube can’t store all videos. Only Youtube can handle the storage cost by using ads due to the massive amount of users. But you could still have a list of links etc. for videos. Maybe stream directly the video youtube but never be on the youtube site. This might already exist in form of FreeTube. It only misses the possibility to view PeerTube vides as well.

I agree. Look at email servers. It just works out. Email server owners don’t look at the content. They just host the servers. Both protocols are federated.

Forums will most likely be driven by the community and volunteers. Just move everyone over to the fediverse. Then it should be easier to find such people.