If you use the .30-06 as your standard, yes the .35 Rem Mag is a "flat shooter". If the .30-06 can take deer at 300 yards with a 150 grain bullet so too can the .35s.
In .35 caliber, the 200 and 225 grain bullet have about the same SD as the 150s and 180s in .30 caliber. This means that given the similar shape the BCs will be the same. The .35 RM can launch the 200s and 225s at the same velocities as a .30-06 shoots the 150s and 180s.
So for deer if a 150 grain .30-06 is good to 300 yards, then a 200 grain .35 RM is also. Same velocity, same SD, just fine a good spitzer w/ a comparable BC.
And for elk, if a 180 grain .30-06 is good to 250 yards, then a 225 grain .35 RM is also. For the same reasons. Again check bullet construction too. You don't want to accidentally shoot an elk at 20 yards with a bullet intended for the .35 Remington (non-magnum).
.35 caliber rifle bullet selection is sufficient for .35 RM and .35 Whelen. Neither of them push the velocity envelope so far that you NEED premium bullets. .35 rifle bullet selection is noticeably smaller than other more popular calibers, but you'll find something that works. Just take care not to use something intended for pistol or .35 Remington.