Flavor – Molasses – “Full Flavor” vs “Mild Flavor”

Nuts are much tastier when they are roasted. Dehydrating may be ok but it will not do the same thing for their flavor or texture.

Nuts have a lot of oil but there is not enough on their exterior for powders to stick to. Of course some of the powder would stick anyway- and with parmesan even more would when the cheese melted. If you are ok with a milder flavor and a lot of powder left in the bowl when you eat them then you could try to use less or no oil.

It is possible that you could make it work with some other liquid other than oil but oil tastes good and won't dry out. Additionally for spicy peanuts, capsaicin is soluble in fat so the oil will actually be intensified.

I don't know about an easier/less messy way because I don't consider this to be particularly difficult or messy. Just toss nuts with oil, then powder, spread on a pan and bake. Doesn't get much simpler than that.

Another alternative that has become popular is kettle roasted nuts. The nuts are cooked in a large kettle with an agitator to keep them from settling and burning. Usually they also candied. The process is much stickier and flavorings adhere much better. At home, oil popcorn poppers with agitators are available that can beautifully make kettle roasted nuts. Manual versions are sturdy and inexpensive.

Salt (Sodium chloride) is salt. As a topping, flakes are commonly used purely for presentation purposes only. The taste is the same, but gets more intense as the salt particles get finer, so use less if the salt is in powder form

As an ingredient, use any form you are happy with, and is economical to use. Once salt is dissolved into water it will be identical to any other form of salt

For health reasons, finely powdered salt is preferable as much less is required to impart a salty taste