Phoenix worms make a good treat, but the claims made about their calcium content are only true for small worms. If you let them grow to be larger, the ratio evens out and the calcium isn't so high. They are an expensive feeder, but good as a variety adding treat. Make sure you puncture their skin before feeding them off because they will go through a cham's system undigested (their cuticle is very tough- they are actually little maggots, afterall)
Hornworms are a bit pricey but are amazing for boosting a cham's hydration. They have a lot of liquid in them and some chams go crazy for them. They are a great treat and I feel like you can use them a bit more often than other treat feeders. I would say 3 a week is about maximum, and that shouldn't be continual. I will buy a pod and feed off the worms once they are large and then wait several months before getting them again. They are a bit fatty, but less so than waxworms. They get very large, very quickly and can have a nasty bite.
Butterworms, I don't know a whole lot about and have never used. They are Peruvian and are irradiated when shipped to the states so that they can't metamorph into moths. They are a potential pest to crops so that has to be done. They are fairly expensive and hard to find without ordering online but make a great treat. They are rather fatty, so one good sized one per week per healthy cham is preferred. I assume you would treat them as you would treat waxworms.