20 L/J are bulk head seats on an exit row:
Pro:
-extra leg room as nothing is in front of you.

Con:
-Exit row seats have monitors in the arm rests so that the seat width is smaller than the standard economy seat and the arm rests do not move as the can in other economy seats

Because of this my wife an I are in 32 L/J going to LHR from CLT so that the monitor is in the seat back, giving more width to the seat.

Main cabin Extra boards with Group 5 unless you have status with AA. Business and First are Group 1,
Meal is standard economy.
Everything must be in overhead bins for takeoff and landing and will be strictly enforced, nothing in your lap since you are in an exit row and will be expected to assist with that function.

I doubt they would let you put your wheelie in front of you, although DFW to TYO I did put my backpack in front of my in the exit row and use that for leg support on time about 15 years ago.

"Refreshments": you will get the standard economy drinks and food service, nothing more. Drinks are free on international service. No pre-departure beverage service in main cabin extra.