When making a cold deli meat sandwich or a burger, does layering the solid ingredients and condiments in a different order change the taste or mouth-feel? If so, how and why? Are there reasons to prefer one order to another? 
Yes, it can change the taste quite significantly.  Here's an easy experiment that you can do:   Make a sandwich, but spread mustard on only one of the pieces of bread. Take a bite of the sandwich, mustard-side up. Take a bite of the sandwich, mustard-side down.   Mouth feel is affected as well, but not quite as dramatically. 