The reason calcium powder is so popular and downright vital is that most folks feed their animals very selective diets. Most herps are lucky to get more that 4 kinds of insects in their regular diets and those insects more than likely have either nothing in their guts or a bit of apple or potato. You could raise multiple species of roaches, crickets, locusts, pill bugs, mealworms, wax worms, superworms, flies, earth worms etc etc and make sure they all are getting fed about as well as you... or choose a few of them and supplement twice a week with powder.
Powder is just more feasible. Never skimp, always buy the best and never over use it.
And of course, if your herps will take veggies then by all means give them nothing but the best and a garden of variety.