Looking back at Scott Speedman’s work in the early days of “Felicity” is a bit surprising. His acting had a wonderfully nuanced authenticity even then. Two decades later, that natural artistry has grown into a charismatic intensity and assuredness. It’s on display this year in the third season of “You,” the eighteenth season of “Grey’s Anatomy,” and the charming indie film “Best Sellers.” When we spoke he had just wrapped films with David Cronenberg and Lena Dunham. He talks about working with those two very different directors, the secret to good onscreen chemistry, how fatherhood might deepen his work, and much more.  Follow Back To One on Instagram (photo by Ben Duggan)