All the 700s are durable, and with a good scope and some time spent on the range, should be capable of taking whitetail sized game at 400 yards. Not all shooters can, and you'll need to find what ammo it likes best of course.
As to the barrel length, most all Remington 700s have 24" barrels in the standard and short action chamberings. Most of their magnum offerings, as well as their heavy barreled guns will have 26".
Real question comes down to carrying weight. If you are sitting stationary, then go on and get a heavy barreled gun. If you are hiking up the Rocky's chasing sheep and goats, then personally I'd want something lighter.