Here’s the deal, YouTube belongs to Google, which makes the content inherently easy to find, unless YouTube doesn’t want it to be. That removes any possibility of you controlling who can see and who can’t.
Peertube is a completely different animal, you have much more control on who has access, in special if you self host.
My confusion with you post is that you say you want it to be hard to find, but at the same time you want it to be “successful”, what do you mean by that? What would make it successful for you?
In that case, and please anyone correct me if you think I’m wrong, I would create a user just for that, entirely divorced from real life “me”, including, but not limited to, different country, gender, age, all demographics, and use this persona exclusively for this purpose.
Know that if you are expecting to monetize directly from YouTube, this is most likely an exercise in futility, but if you you’re not concerned with that, you’re golden.
I would make sure to upload always over a VPN, just for good measure.