There is also LibreTube that comes with SponsorBlock
Sometimes videos are not viewable on a specific instance, but this way you can keep all your subscriptions and other settings even when switching to a different instance.
If I understand what you are saying, Piped has this. For example I can stream from instance-1.com but at the same time I'm logged into instance-2.com so that I can keep my favourites and settings. See "Instance" section here https://piped.video/preferences particularly the option "Use a different instance for authentication"
Also, I would not call it "adblock". It just comes without ads out of the box, just like most comparable apps.