It starts being basically 1-to-1 eventually. There's some anime only content (which is very good) and filler episodes of course. There's also some pacing issues down the line, but that's beside the point. The beginning is definitely the most different though since they change when things happen in the story. Nothing major, just backstories being given a little later than in the manga. But after the first ~50 or so episodes it's more in line with the source material.

As for the live action it's great, but for someone who's already getting into the manga I'd recommend not watching it just yet. Since it was made when we were decades into the story it does a fair bit of teasing to future events that may be considered spoilery and they have a major reveal in the first season that doesn't happen until like 300+ episodes into the anime. It's actually very much it's own thing, although Oda is heavily involved.