The 3 most important things when killing elk are: shot placement, shot placement, and shot placement.
"Energy" isnt even worth talking about.
IMO/E, young shooters consistently shoot smaller, lower recoiling rifles much better...and that pretty well applies to everyone else.
I shoot my 338 well, but its flat not a rifle I go to the range and practice with much. Its no fun to shoot.
On the other hand, I take a 22-250, .243/6mm. 7-08, etc. to the range, those rifles get shot a lot more. The more you shoot, the more comfortable you get, the better shot you become...again, thats across the board.
Sooo....with that said, I've been shooting a 7-08 as my primary rifle for the past several years. Its easy to shoot, fun to shoot, and it flat shoots very well.
I shoot the 140 Accubonds at 2850 FPS and have taken elk, deer, bear, and pronghorn with it.
Last week, I shot my 14th elk with my 7-08, my brother shot 2 with it and a friend shot one with my rifle as well. Shots have ranged from 70 yards to 621 yard on elk.
I loaded up some 120 grain Ballistic Tips for nephews 7-08 and he's killed an elk, 4 whitetails, and a pronghorn with them...all one shot kills. I have a mild load that shoots the 120 at 2825 FPS...recoil is minimal.
IMO/E I would recommend the .243, 260 rem, 7-08 etc. line for starting kids out. If you handload, you can start with the lighter bullets and mild starting loads. When they get more comfortable and older...make the adjustments as needed.
My 2 cents...