Psst... if you sign up to their Premium tier you can play songs from their "Community" (i.e. user uploaded songs). If you sign up to the "Pro" tier, you can play even more songs that are normally locked from their catalogue (but you'll have to manage rightsholders authorization yourself).

Yes, the free songs on YouTube aren't customizable: there's a low voice guide that you can't turn off (or turn up...), and you can't change tempo.

You can do this from their huge catalog of songs, using their official app or their web client: https://www.karafun.com/web/

Plus, they have music quizzes you can play with many people using smartphones as remote controls. It's super fun for parties where people don't want to sing all the time.