If you do not have priority status, and you want to carry on your bag, you sometimes maybe SOL. So my tip is while sitting in the back and next the window may not be your first choice it will get you on faster. Would you rather be in the back and wait to get off the plane or stand at bagage claim? If the window does not sound cool to you, and you carry on and your bags cannot fit. When the agent checks your bag at board, you are usually not charged the $25+ fee. The crew just wants to check that bag, and take off. They dont have time to worry about the details of the bag fee.
Happy trails to you! And Safe Travels