I use the same thin leather gloves as in summer or thin fleece/leather gloves as in autumn/spring. By that you get the best out of muffs and heaters and touch and feel on grips. Of course if the muffs doesn't have proper insulation and wind protection you are not able to use thin gloves, even with heaters. I my need to use heater position II if it gets down to -20C or so but otherwise position I is enough. The more you have insulation in (on?) gloves the more you loose the effect of heated grips.