The 265/75's will be 3.9% bigger. So when your speedo reads 65mph you'll actually be going 68mph.
265/70's are only 0.5% bigger, so they wouldn't give you much extra clearance.
You'll lose a little mileage on the wider tires, but gain a little by making the gearing a little taller. Probably not enough either way to be of concern.
There will be no significant effect to braking, and the you'll probably be 0.1 or 0.2 seconds slower on your 0-60 time, which is probably over 10 seconds anyway.