Chemotype inheritance is one of the few traits that behaves like a textbook example, since crossing a high THC plant with a high CBD one gives offspring producing both in roughly equal amounts. The following generation splits into three groups, and only lab testing tells you which plant sits where. How that segregation works, with the ratios to expect, is set out at https://breederregularseeds.com. Judging chemotype by appearance is not possible, whatever a seller claims.