The 65. Creedmoor is a .308 length cartridge and will not fit an AR-15 length action. It would require an AR-10, same as the .308. The 6.5 Grendel and 6.8 SPC are both designed to fit a standard AR-15 length action.
Here are some size comparisons. 6.5 Grendel on the left, 6.5 Creedmoor on the right:
6.8 SPC on the left, 6.5 Grendel on the right:
The short AR-15 length cartridges are, at least in my opinion, pretty marginal for deer hunting. I know guys use them, but they do shoot kind of light for caliber bullets at pretty reduced velocities. Maybe good for young, recoil shy hunters for small deer at close range, but I honestly think there are better options, like a bolt action .243 or something. Or a bolt action in 6.5 Creedmoor.