I think multiple accounts is a great idea.
I work in tech security and I cringe in pain when I see people post their 10 year accounts. The amount you can deduce and learn from mined social media data is absurd. I migrate to a new account every 6 months and that's the longest you should keep an account. This of course doesn't apply to your public brand account.
The clever check is impossible. The server can't know the client is showing the video even when playing DRM content. I could literally mute the sound and put a black box over the ad until it's over. The problem is as old as the internet itself.
That's why Apple and Meta pushing eye tracking so hard. It's the only solution to the ad blocking problem.
I think YT is doing well with YT premium and that's the way to go for them. It's one of my favorite subscriptions and I'd probably stick around even if they raise the price unless they hurt the creators so badly they bounce and I'd bounce with them.