I've got experience with this, if the animal is used to being handled on a regular basis, they wont react to the flash. HOWEVER, if you have animals that arent handled often and live in rack systems (from my experience) they will twitch when the flash goes off. Its not painful to them, they dont strike but they almost jump. Its just because of the sudden increase in light. You'd jump too! They get used to it after a few fires though.
They do definitely restrict your angles (the tents) BUT, they also kind of help keep the snake corralled and in an area for you to photograph without getting stuff in the background.