Yeah, CMH lights will need the ballast as well unless it comes built into the hood. a 2×2 will need some good ventilation, even with the low wattage. It can increase the room temps up to 9 degrees, depending on the light fixture.
I have 2 xxl air-cooled hoods with CMH converters using Philips bulbs. I run an inline fan through the hoods to help cool the lights more.
