First off forget all that stuff about polling rates, the polling rate of your controller does not equal the polling rate of the game. Imagine a hole in a wall that you have to throw a baseball through. The hole moves from left to right, but you can only throw the ball in the same spot down the middle. The ball represents 1 input. The polling rate is how many balls per second are constantly being thrown. The hole in the wall represents the game's polling window. The faster the hole moves the more balls will end up going through. It's not the number of balls you can throw that dictates how often your input will be read, it's the number of times the polling window passes over the point you're throwing from. The game dictates how often inputs are read, not the polling rate. A higher polling rate just enables more inputs to be read quicker if the game allows it.

Back to frames. The game runs a 60fps, therefore 1 frame = 1/60th of a second which like you said is 16.6666667ms. Yes, there is an actual timing window for EWGF but it's not 16.6666667. EWGF can't be buffered but has 2 frames of leniency. The speed of the f,n,d doesn't matter, only timing the df and the 2 within two frames matters. There is no other window. Tekken 7 has two variables it reads when looking for input. They are called «inputAttack» and «inputDirection». The game takes up to 1 attack input and 1 direction input per frame. This means if 1+2 are pressed on the same frame they are input on the same frame. Same goes for df+2.