If you stick around for even part of some post-screening festival Q&As with directors, at times you can get the feeling they’re expounding on the film they intended to make rather than the one you’ve just seen. But Jesse Eisenberg is nothing if not hyper-articulate. He describes the essence of his delicate second feature, A Real Pain, as a consideration of “epic pain vs. more modern pain,” and how to reconcile the latter against something as monumental as genocide or historical trauma. What’s surprising is that he achieves this with a deft lightness of touch in a frequently laugh-out-loud funny odd couple road trip movie whose emotional wallop sneaks up and floors you. Eisenberg’s perceptive script — rooted in his family’s history — shares some thematic territory with the multihyphenate’s second play, The Revisionist, in which he starred off-Broadway with Vanessa Redgrave in 2013. It’s about the conflict of Americans grappling with their own troubles, however minor, while attempting to be mindful of the punishing experience endured by ancestors from traumatized cultures — a Holocaust …