Does Pi-Hole disrupt anything important?

I ordered a Raspberry Pi 5 so I have a Pi 3 that’s about to be redundant. I haven’t used Pi-Hole so I was thinking it’d be good for that but I’m curious if there’s any downsides for users. Are sites blocked if you dont whitelist them? That sort of thing.

Basically, I’m not worried about me having issues but I’m worried about a maintenance headache if friends and family can’t access things.