Re: 270wsm vs 7mm wsm vs 7mm ultramag
If only a choice of 270wsm vs 7mm wsm vs 7mm ultramag, and elk is the quarry, I would opt for the ultramag. Elk are big, and bullet placement on elk isn't always perfect, so the extra power helps — some. For the other game, an ultramag is a bit much. Too much cost, barrel erosion, muzzle-blast & recoil for most to be comfortable with.
Between the .270 wsm & 7mm wsm, I would opt for the .270 only because the 7mm wsm has been dropped by Winchester and factory ammunition may be less available in a few years. Otherwise the differences are negligible.
A .270 wsm is a great all-round cartridge that will take any of these animals but I think you posed the wrong question. The right question in my mind would have been, "Do I choose one of these or jump to .30 cal?". If that question was posed, I would strongly recommend jumping to .300 Weatherby or .30 wsm because both handle heavier bullets than the .277 or .284 cartridges, and heavier bullets are a real advantage when the perfect shot doesn't present itself, or you don't succeed in making the perfect shot.