One map cell is (by definition) a space of VIEW_W x VIEW_H pixels. (Those have default values 640 x 360, respectively). So changing VIEW_W and VIEW_H will change the size of map cells. (The cells aren't used for anything special in the level editor other than acting as a guide)
The views (and menu rooms' sizes) won't automatically adapt to this new size so if you change the view size you will need to change those as well.