You need one guy from each, but I’ve never mandated that one guy has to be a starter, though that’s what I’ve always tried to do.
When I check rosters all I’m looking at is to make sure the team and positions look the way they should, but if say you had the Phillies as an OF team and you took 21 Bryce as an OF but used him as your 1B if say you didn’t like your 1B team, as long as you had a back up from that team so that they’re represented that would be permissible