Our policy was supervised / filtered only until early teens. Kids sites, educational stuff, games we purchased and approved of, etc. We were also late to give them phones, our son got his first because in his freshman year of high-school his band teacher set up a boiler-room to sell worlds finest chocolate and he was the only kid who didn't have a cell phone.

When we had "the talk" we discussed masturbation and porn, why porn is popular, and all the negatives that go with it without condemning it outright. We talked about online predators and not sharing things with people you didn't know, especially pics, addresses, etc.

My wife and I are firm believers that kids need space to discover who they are, so as they became teens, things went to semi-supervised. We paid attention to them more than their devices, but we had rules such as adding one of our emails as a recovery address to any socials they set up, so we could check up on them if we thought something bad was going down. Never had to use that, and I think just having it there made them think about what they did online.

Around sixteen/seventeen, no filter and no more backdoors into their accounts. Just a couple of long heart to hearts about how shitty things can be on the internet and how we're there to talk with no judgement if they need us.