You must specify the size of sole that you want, otherwise they will send you the most common size. Yes I had to cut the toe end thermo sole to fit my boot, there is a maximum cut line printed on the sole, I have normally an extra insole in my boot which I took out and fitted the thermos sole in it place, therefore no discomfort under the foot, upon initially inserting putting my foot in my old boots they did seem a little tight on the top of the foot, but after a couple of steps I guess the thermo sole settled into position and no other issues.
Like I wrote in my first post, you dont really notice to much heat as they are designed to keep your feet at there normal body temp, at best you notice a little warmth under your foot. With the remote you can scroll through stand-by, medium, high and back to standby, these thermo soles are just like a thick inner sole at the heal and a normal thickness inner sole under your foot and toes.
I have only worn them once so far and even though my fingers were feeling the frosty temps, my feet had no issues!