There is no such thing. I can only refer to the gazillion "How to optimize performance in AE?" threads for detailed explanations. The short version is, that AE barely even uses GPU acceleration, is barely multithreaded, does not use any fancy asynchronous parallel processing and on top of it is further restricted by general limitations of working with video like linear, sequential file access to produce temporally consistent results. You can't change any of that.
I did went into the scripts for premier to allot more processing power for exports and added 10% more power (kinda scary but it worked). But that is multithreaded and cuda enabled. I guess there isn't an option for that for in background processes in Ae and Pr.