My YouTube is ad free, although that isn’t the pihole as far as i know. The most noticable effect is lack of ads in Samsung apps like the broadcast tv guide. I will say that Samsung is a bunch of assholes since they try to process more than 1000 requests per minute and i see that in the pihole log.
I run a pi hole and it blocks 1000 attempts per minute from a single Samsung TV, then it outright denies requests from the tv. Duck those douches.