Tape the airgap between the fan and the drywall around the fan in the attic when you install it. Also insulate as close as you can to it and over it if allowed by the manufacturer for that fan. The trick is to avoid attic air infiltration that will cause moisture to condense on top of the grill and around the fan and next to the ceiling. It will cause your paint to chip off and replacing 2" of popcorn ceiling all the way around the fan isn't much fun.
They also require maintenance. I lived in an apartment complex that cleaned them yearly. Just like your furnace motors, etc, the grill, fan blades, and fan motor will fill up with lint, dust, etc that destroys its effectiveness. It can get into the motor windings and bearings over time. It doesn't blow out but usually sticks to the point that you have to wash with soap and warm water and use a toothbrush. Some bearings need a drop or two of oil each year. In some homes you may need to clean them sooner. Look for the lint on the outside of the grill. They will plug up before you know it. You can also buy replacement motors and fans if they are to gummed up to clean.
If the fan gets noisier than usual, they can plug up till the bearing gets hot and causes a fire. Seen that before. Good luck.