AFAIK, the original fitments on all CX5'S are Toyo, not Yokohama. I've replaced my Toyo's with Michelin Latitude Sport 3's, they are a definite improvement. Having the AWD version, it's generally accepted that you need to use the same on all four wheels.
As for front or back, I always understood that new ones should go on the rear if the car is front wheel drive. This is because when the rear looses grip on a front wheel drive car it is usually on turn in or mid corner when the driver backs off (puts more weight on the front wheels) - it's basically lift off over-steer; this can happen very very quickly and the car snaps sideways then the only way to save it is to floor the throttle. As the driver has already backed off for a reason is likely to be the last thing he will think to do so the car over-steers off the road, or spins in the face of oncoming traffic. If the front wheels loose grip, it usually running when wide on the exit of the corner. The driver can simply back off the throttle, and they will slowly and predictably regain grip. Someone who used to alley drive told me this about 30 years ago, I've heard this from a few other sources as well. I also believe some tyre fitting companies do this as well?
Alan