My question is, can you switch a hidden ability to a non-hidden ability? If you can, then say the Pokemon has two normal abilities. Which will it change to? If the Pokemon has two hidden abilities, then can it switch between those two?
Ability Capsules will not change any Pokémon's ability to or from it's Hidden Ability.
Also, no Pokémon has two Hidden Abilities so no, if your Pokémon has it's Hidden Ability it is stuck with it's Hidden Ability. The Ability Capsule will only work on Pokémon who's species has two standard Abilities.