Some schools will post their new team rosters in the Fall, which will then could be reduced by the Spring season when they have their official roster. You have a window of opportunity now in the Fall to look at all of the school rosters posted and even do some research into the archive page. Look at playing time and retention to see how many players are there 3-4 years.
It's debatable whether having 40-50 players is reflective of a strong program or if the coach is really good at luring kids to enroll in the school in the hope that they will play. Many D3's are smaller Liberal Arts schools and they get incentives or have goals to recruit kids to enroll in the school, regardless if the kid ever sees the field. Some of the stronger programs are notorious for a roster churn and want to start with as large a group to cull from as possible.
Fully agree with CabbageDad and ILVBB that the best thing to do for any school a kid is seriously considering is to go visit the campus in the Fall and observe a fall practice or scrimmage. There is so much to be learned from the visit that it is well worth the cost if it involves travel. Beyond assessing the competition and team dynamics, you gauge the coach's true interest during the visit. Most often they will set up a class to attend, lunch with the players, some even allow an overnight visit in the dorms. This was all a huge asset to my 2017 as he was sorting through the really interested programs.