After checking with Chinese phone repair shops, which has large volume of business and a lot of experience on the subject matter, these are what they found.
iPhone 7 screens are more sensitive to individual variances and screens made by different suppliers like LG,Toshiba, Sharp have different sensitivity, in the factory the phones are calibrated on the line so there is no problem. However depending on how you've swapped the screens, you may encounter ghost touch or insensitive screen.
On the backlight plate, assuming the screen is not a Chinese workshop remanufactured unit that Frankenstein parts together,
Toshiba screens have manufacturing code beginning with C11 or F7C,
LGs have DTP or C3F,
Sharps have DKH or C0N,
Crossing between Toshiba and Sharp gives you about 5% chances of bad touch, while crossing LG into or out of the equation has around 50% chances of ending you with bad touch because LG sensitivity range distribution is very different from Toshiba or Sharp. Without the official Apple calibration magic box, it is very likely to not work properly if your phone is built with LG screen but reinstalled a different one, or the other way around.
So that magic calibration box has its value after all, unlike Louis Rossmann said it is just there to !#^& 3rd party workshops off.