Magnums are not that different from regular handguns. Magnum rounds have more muzzle energy, but they also cause more recoil. For general use, non-magnum ammo is good enough. That’s because, as long as your bullets can penetrate, shot placement and speed matter more than some extra kinetic energy from magnums.
Rifles and shotguns still have more muzzle energy than magnum-firing handguns. For example, 5.56 fired from a rifle (20 inch barrel) still has more energy than .44 Magnum fired from a revolver (7.5 inch barrel). (Note that fudds whine how 5.56 is underpowered, meanwhile a .44 Magnum revolver used to be Dirty Harry’s “the most powerful handgun in the world”.) Additionally, rifle bullets typically penetrate better than pistol bullets due to their shape.
Rifle caliber pistols are gimmicks. (Unless you mean actual rifles that are only considered pistols by silly US gun laws. But for those, you would use both hands and preferably stocks, arm braces or other support. A shield would interfere.)