I am not asking about which pre-enchanted/plot-related armor. I want to enchant armor with +x to sneak. I've been crafting leather armor for this purpose, but am wondering if using basic clothes would help my sneak abilities even more.
The strength of the enchantment you can apply to an item doesn't depend on the item's quality or armor/clothing classification, so you should be able to apply the same Fortify Sneak enchantment to light armor boots as you can to shoes.
However, the weight of what you're wearing does affect how much noise you make while sneaking, which in turn affects how easy you are to detect, so you might see some benefit from using clothing instead of light armor (though your movement noise can be lessened or eliminated with the Muffle effect). This answer has a lot of info about how sneaking works.