I personally would use the same load to hunt coyote as I would to hunt deer. No need to resight for a different load. Also, given that most 270's were made to shoot bullets in the 130 to 150 grain range those 90's may not even shoot that well.
Given the power of a 270 I would think even the lightest bullets would tear up a coyote.
With really light for caliber bullets you may start out with a much faster muzzle velocity, but it will fall off fast due to a low BC.
Hunt fish is exactly right. I also agree that you would be better off using a 130 or 140 gn soft point bullet for coyote if you care about salvaging the pelt. A 90 grain would explode big time, there wouldnt be much left to salvage. I once shot a red fox with a sierra 130 gn spitzer out of my .270 and the entrance was a pinhole, the outty was not even an inch in diameter.