Never heard of a 10 twist 6.5 CM. The whole point of 6.5 CM over 260 is to get a faster twist barrel. 1:8 is pretty standard with some 7 or 7.5 twists barrels.
H4350 is the go-to powder for most if they can find it. Other good substitutes are Ramshot Hunter, IMR4451, Reloader 16,and 17 both are mentioned a lot too. Especially with heavier bullets. You might find other powders work well with 110-130 gr bullets. For deer a 120 would be fine, if hunting game bigger than deer you might want to go to 140's. Or for long range target shooting the 140-150 gr high BC bullets
If it is a 10 twist you'll probably want to stay with 130 gr or lighter bullets. It might shoot 140 gr hunting bullets OK, might not. But it won't work well with target bullets much over 130 gr.