I had 255's in a 2012 flhx and that was the coolest running bike I've owned. It was tuned with the sert. Not to say 222's wouldn't be cooler running because I really don't know. I believe 255's can be tuned to run without excessive heat.
The SE 255's are called a smog cam because they pass EPA and come stock in the CVO models, they are not much more then a stock cam, the intake duration is only 211 and the intake valve closes at 25 I think, very early so it makes torque early but will fall of after 4,000 rpm, plus the a overlap of only 13 will make more heat. I put in the SE 204,s, in my opinion a much better cam and pulls past 5,000 rpm, I tried different cams and like the SE 204's the best, if you are deciding between the 255 or 222 I would choose the 222, it is a very close cam compared to the SE 204.