Allies and Powers and the difference are discussed in the first few chapters of the first book.

Don Juan’s ally, the little smoke, helped him ‘watch and see’, told him what to do. It was used for personal reasons. Similarly, the Devil’s Weed could be used as an ally but was not Don Juan’s ally, but his benefactor’s. The ally protects.

Mescalito is a Power, a teacher and cannot be used to protect.

Inorganic and organic beings are introduced much later in the works. To be brief, they are awarenesses that help you shift your assemblage point. Some do so in dreaming. You have to conserve enough energy to be aware of their presence.