Are online ticket prices the same as in-person ticket prices or are there service/convenience fees for online purchases?

The prices are the same! ;)

There’s service fees if you buy through fandango or atom

Yes

There are usually service charges for online purchases. They’re usually worth it because you can guarantee a better seat for a popular movie. If the movie isn’t popular at all, show up when the movie starts and you’ll still get a good seat! This has happened to me.

There's a service charge for online purchases