positions are fairly fluid. It'll be better to have your best players on the court, so having too many guards is ok. Definitely preferable to too many bigs.
IIRC, there isn't a shortage of a particular position. However, certain positions seem to fall into a particular type of player e.g. Most PGs that signed up are playmakers.
probably some worth in signing up as a Jumpshooting Big man or a Scoring PG? don't think many would have taken those roles
From what I have seen I might steer clear of being a Point Guard, particularly a playmaking Point Guard.