It wasn't entirely clear, but it seemed to just be his proficiency at utilizing others' powers. It's nothing flashy and difficult to really call a "superpower," but as far as I could tell, that's it.
Do you think there is any benefit to watching this before the series, or is the series just a longer and presumably…
Really late response, but the movie is the original concept for The Gifted. You can see some things that made it over to the show (namely a few characters and certain scenes), but overall they tell two different stories. They both tackle the idea of students with special powers fighting against a corrupt school, but the series made a lot of changes to the setting and plot. It won't feel like watching the same thing twice.