That is a great elk cartridge, and will work great for your uses. Just plan on getting some good range time with it.
If you want to get to 400 yards a holdover reticle could be really usefull. Lots of companies have them. I like a few of them including the HHR reticle from Sightron, Dead Hold BDC from Vortex, and the Rapid Z reticles from Zeiss.
You don't need much magnification to shoot accurately to 400 yards, or even farther, so something in the 3-9, 3.5-10, 4-12 range would be ideal I think. That will keep your exit pupils sufficient for calibrated reticle use in low light.
Here are three good options (not in any particular order):
Sightron S2 Big Sky 3-9X42 or 3-12X42 w/HHR
Vortex Viper HS 3.5-10X44 w/ Dead Hold BDC
Zeiss Conquest 3-9X40 w/ Rapid Z600