I do mine vertical.... I sat in a doctor's office the other day, close to a switch, and tweaked the screws with my knife. I do get OCD about that, same as with toilet paper. Only 1 right way.
Glad I'm not the only slightly OCD electrician around.
I go with vertical, like in the big color photos in the manufacturer's catalogs.
The paper always faces out, not against the wall (top-feed). Keeps the wall clean.
The guys I learned from didn't give a rat's __s and thought I was crazy with my torpedo level and narrow slot-head driver...
As far as brands/sizes of plates, sheesh, I'm lucky if all the plates in one room match when I'm doing a remodel.
I particularly take care making sure my load centers are plumb and the screws holding the covers on are all lined up with vertical slots. Nothing I hate more then sloppy work when it's the service equipment.
As far as clients, I find that the more they're spending, the more they notice the details. Over the years, many of my clients have noticed (but my wife still doesn't).
My daughter and my cat both DO. One of them is still unraveling the toilet paper, not sure who...:roll:.