Your not comparing the same weight bullet...so of course the .300 would have more energy...
Of course it will.
Given the same case but different bore diameters the larger bore will be able to fire a heavier weight bullet at equal velocity. Or it will be able to fire equal weight bullets at higher velocities.
So, the 300 would have higher velocity and higher energy that the 7mm or the .270 either way you look at it.