Though one’s now starring in a drama, the other in a comedy, Lizzy Caplan (“Masters of Sex”) and Allison Janney (“Mom”) have both famously spent time in the other category — and agree that the lines are now getting blurred. Their back-and-forth banter at Variety’s “Actors on Actors” studio proved the point, as the actresses chatted about the thrill of doing theater, and the emotional toll of getting into character.