As a general guide, substances should be in their freebase form to be smoked, and in their salt form they are better to consume orally.

That being said, there are some exceptions and some other aspects related to this. For example, a lot of people smoke changa using caapi leaves which havent been freebased. The caapi leaves themselves contain harmalas in salt form (which exact salt is unknown), and yet they are successfully smoked.

Smoking certain alkaloids in certain salt forms may work because the energy from the lighter might be enough to simply dissociate the acid ions from the alkaloid. But we generally say to avoid this and only smoke freebase alkaloids because more often than not, smoking alkaloid salts won't be effective or might even be dangerous for the following reasons:

1- The salt form of the given alkaloid may have a too high boiling point
2- The alkaloid might break down during combustion instead of vaporizing
3- The combustion could generate irritating/toxic byproducts (for example when smoking fumarate alkaloids, it can lead to the formation of maleic anhydride, hence why we really don't ever recommend fumarates)