30% is more than the body is actually likely to absorb and much of it gets peed away so it's no waste of your money to "only" have that much. I don't know about Reptical because I don't buy that brand, but both Rep-cal and Minerall have good mineral balances and more calcium than most herps are likely to absorb. Giving higher amounts of calcium increases the likelihood of kidney or bladder stones and/or visceral gout if there aren't enough of the other minerals and those conditions can trigger MBD in spite of high calcium intake. I don't like Reptical because it contains fat-soluble vitamins that can be toxic in overdose.
As far as gutloading goes, that depends on the type of prey. Giving enough calcium to mealworms to try to right the 1:9 calcium to phosphorus ratio is fatal to them so it's impossible to effectively gutload them. But crix, roaches, supers and silkworms can all be gutloaded with calcium quite well.
The Zombie Mama is here!