Hello! My opinions:
-The question is "What differences can you see?" 99% of photographers won't see any difference in term of sharpness between APS-c and FF.
-Theorical differences are well known: a/ dof b/ low light situation. That's all.
-lens,PP and uses are as important as the camera itself.
-Don't worry about sharpness. Don't waste your time reading charts, graphics and so on. Learn how to shoot a great photo.
-99% photographies on the web are post-processed.
-Choosing a brand isn't a simple question of sharpness: menus (as you say),sustainability, roadmap, warranty, community, personal feeling...