with regard to treats, I give treats to my horse and he can become a bit mouthy, however he immediately goes back to respectingmy space if I reimind him . My friends horse is not polite about takingthem from my hand and has inhaled my whole hand more than once. So, for him, I dig in my pocket and he gets all attentive, but I move my fingers in the air at the side of his head and say "over!" He will move his head away from me and wait for the treat, which I then place on the ground in front of him. He learns to WAIT and he gets a stretch to go down and the endorphins that come with lowering of the head.
The thing about treats, is make sure you are using them as a reward, not a bribe. There's a big difference.
When mounting, if Mac comes and stands nicely for me and doesnnt walk off when I am in the saddle, I reach forward and give him a treat, but not always or he is only performing for treats. Just someimes to keep him interested in cooperating. I never give him the treat ahead of mounting , like, "here, take this and then you'll be good" That's a bribe.