I always run cold and find the burner parka over a single merino base layer a bit too warm if I’m moving at all above zero. Stationary that’s good to well below zero as long as the lower body is kept warm (down pants) and not sitting on a cold rock.
Last year during below zero hunts I wore a super down ultra jacket for moving and burner for stationary. If I didn’t have warm pants on I’d get cold even with the burner when not moving.
Also I bring a big pack (MR Pintler) day hunting so I can toss the burner (and my sons’ puffies) in easily. I’ve only put it in the included stuff sack once and that was like stuffing a sleeping bag.