Other forms: theoreticians
Someone who comes up with testable ideas about how something works is a theoretician. Theoreticians study all kinds of subjects, from social science to art to games.
A theoretician is someone with a theory—and a theory is a set of beliefs that can be tested (although they may be untested so far). The Greek theoria, "contemplation or viewing," is at the root of both words, from a root meaning "to see." In the social sciences, a theoretician might analyze society through the lens of economics, and in chess, a theoretician studies and writes about the theory and strategy of the game.