Group demostration only cover 18 players only. Why don't you use "scouting combine"?
Both would cost you 20 points. Then spend the remaining 8 points for interviewing 3 or 4 players.
but 3-4 interviewed players are very few when you invested already 20 points for player info. using both you should for sure invest more than 28 points in total to really "use" all the information you got
only using group demostration you might interview up to 9 players with 4-5 star rating.
for me the potential is the most important information for the draft followed but age. i don't care about the height.