Where is the best place to learn about bits! I want to learn all I can. About gag bits curb  bits snaffle draw bits any type. Any good YouTube videos that explain or books. 

I'm in a Facebook group called "Horses:Proper Bits and Bitting techniques". There is a LOT of information in the files about how bits work, the physics, order of operation and such. There is a lot of knowledge in the group from all types of disciplines. If you join - never -EVER- advertise that you are a barrel racer. They can be brutal on us. Just lurk and learn. Then decide on how you want to apply what you learn. DON'T get into arguments. You won't change anyone's mind. Just lurk and learn.

This is a great article: https://barrelhorsenews.com/equipment-use/training-secrets-to-a-soft-mouth/?fbclid=IwAR1KCUZL9vFSXOLZGL_hOQj3qyOd_etvTaQG1eShTqrFNt70yaCn3otaZ0w

Also, look on YouTube where Dana Kirkpatrick and reiner Casey Deary ride each other's horses.. There are two parts to it, and a third video explaining bits. All of those are REALLY insightful!

And, Jordan Briggs has done some videos on Facebook of what she uses and why.