Practice at the U16 level is a direct reflection of the coaching staff. If your coaching staff is chaotic, practices will be chaotic. If your coaching staff is disciplined then the practice will be disciplined. Its the 1 time your entire coaching staff should have full control and attention of all the players on the ice. Far to often at the 16 level entire coaching staffs don't show up (Only 1 or 2 coaches at practice but a bench full at a game).
You also have to consider the amount of players on the ice. With large rosters you are almost forced into Flow drills to keep all skaters moving but you also need your coaches correcting issues during those drills (back to the above statement about all coaches being there). There are some very good Line/Flow drills out there that can keep practice moving AND have lines play together.
There is no replacement for small area games. Most FS 16 teams will have 2 if not 3 goalies, get 3 nets in the corners, play 3 on 3 for 45 seconds at a time, that's 18 skaters moving at once for 45 seconds. You will need 3 coaches but this allows you to have lines work together and keep everyone moving. We used this one at the college level and was very successful.
Don't forget practice is a reflection of your coaching staff planning and teaching capabilities. Not all coaches can teach so go watch some well known coaches in your area and copy what they are doing.