I'm setting up a server with my friends, and I'm including this mod in my modpack (we're doing Vanilla+). The one issue is I find the prismarine armor set to be OP, and I'm trying to configure it out, but I'm unsure how exactly to exclude the one armor set. I found the "overwriteValues" part of the code in the config section, but I'm unsure what I would put there to disable the prismarine armor set, or if that's even the right place. Thoughts on how I could exclude it?

You cannot do that. You could, however, remove the recipe.