When I got my journeyman's card in VA last century, you'd have been laughed out of the building for even asking about 'proper' plate screw position.
As for the ground, you had a union background if you did ground up as that was DC code (Washington) and pretty much only union guys worked DC. If you didn't have a union back ground, you did ground down.
The reasoning goes like this; ground up, if something falls down a wall, say, a ladder or something capable of cutting into the cord, you wanted it to hit the ground first as socket mounted ground up meant the wires within the cord were such that the first conductor something could cut into was the ground.
In non union circles, the reasoning was that if something fell to knock a plug out of the socket or it fell out, gravity dictated that the last contact point to break would be the ground, thus, ground down receptacles. Also, if it is loose and kinda sagging, it is possible that, ground down, the hot and neutral can be exposed a bit.
I do ground down. When I see ground up, I think 'union guy was here'.
There is valid argument for both. Some extension cords are made so that ground down helps support the thing a bit better and help keep it from falling out.
6 on one hand, half dozen on other.