Firing off the ball
Tennis Ball Drill and the aforementioned board drills are good.
You can do all the drills in the world vs air or pads it all doesnt matter when they actually have to hit someone, who wants to him them back.
Michael's 2 board "self teaches" your l.e.g progression
Your splatter drill likely teaches to leave their feet bc your teaching them to fall into padding. Just natural response some dont realise. If you tell your kids to tackle and land on top of ball carrier, youll have a lil more leg drive in tackle then before.
I can explain it to you, I can't understand if for you.