Reference snow and training-here in Colorado a lot of us use Huff-Grip
snow pads fitted under a standard rim shoe. Despite riding in most
weather conditions short of all-out blizzards, I've never had to put borium
or caulks on their shoes for extra traction. The Huff-Grips flex the
snowballs out as they move along. Just keep checking under the pad
itself since it can get a bit wet and thrushy under there, also occasionally
pebbles, etc can work up under the opening in back and throw your
horse off. I love winter riding around here as there are very few other
humans out on the trails. Enjoy!