If you want to pull the plug and add fluid through the top while its off until it starts to run out the side that would be easier than filling it through the plug hole. You still going to need to get under the car. You need to invent a shifter dipstick.
You shouldn't be able to see the top level of the fluid. Its open between the two areas, what you see is what splashed/slung around and sat from the last drive and is normal. Yes, it is an easy place to fill from with the high plug open underneath.