I’ve been looking for this info and couldn’t find it, so here it is. I’m on a Mesa (United) CRJ 900 with 9 first class seats. I’m in 4A. The seat itself is a first class seat (in terms of the construction of the seat itself), marked as E+, no first class service. There is no solid divider. Backpack is fine under seat in front. Overhead bins on CRJ 900 will not fit a standard roll-aboard. No WiFi. No power near seat.