1. I would NEVER put a Tom Thumb in a horse's mouth. But that's a whole different discussion that has been talked about many times on this forum...how bad they are.
2. I ride in ported bits with a swivel shank...like correction bits, grazers, spoon mouth, even a lifter bit here and there. I own one snaffle bit and I use it when I want to do some schooling that requires more contact. I have WP horses so it's usually a ported bit.
3. Then there are times when I just drop the bridle entirely and school with nothing whatsoever on the my horse's head.