He has played centre midfield and Number 10 quite a bit for the youth teams, moreso the latter. He always did well there: He can pick and time/weight a pass, but he's never going to be elite at it.
He was unbelievable on the right at the U17 European Championships playing as a right winger. He absolutely killed it in transitions. He scored a goal a game at the tournament and did the same in qualifying too--finishing top scorer overall.
Nelson's best quality is his ball carrying. He can run as fast with the ball with it as he can without it. When he zips with the ball in transition, he's frightening. He's not elite in terms of ball manipulation: Beating a man from a static position is something he can do and do well, but he's not quite Jadon Sancho in that area of his game.
I've always thought there's a similarity to Chelsea's Willian, only without the hopeless final ball and finishing of the Brazilian.
All that said, right wing or left wing is where he'll end up. It'll be interesting to see in which direction his game develops and which wing he settles into. Short term, as in next season, it's right wing he'll fare best at though.