I recently re-read the owner's manual and the recommendation is this: "Pre-heat smoker for 30 to 45 minutes at max temperature before loading food." I take this to mean that the MES should be fired up to 275° before opening the door and putting the food in. Other guys on SMF have recommended the same thing since my MES 30 easily loses about 50° of heat every time I open the door to insert the AMNPS or put food in or whatever I need to do that keeps the door open more than 30 seconds.
However, I've seen just the reverse that you've seen using my Maverick ET-733. The MES temp display is always higher than the ET-733, at least 20 degrees or more. I go by the Maverick and not the MES display.
As for cold smoking I always keep the MES 30 unplugged and I use the AMNPS. That system's worked great the 3 times I cold smoked.