Furthermore, does iPhone 6 Plus and 6s Plus use the same screen?
Same size and resolution display but iPhone 6S Plus adds 3D Touch. The iPhone 6 Plus was the device that took Apple into phablet territory with its 5.5-inch display. The iPhone 6S Plus sticks with the same size, but it features what Apple is calling 3D Touch.
Similarly, is iPhone 6 Plus and 6s plus the same size? Both the iPhone 6s and 6s Plus are slightly bigger than their predecessors the iPhone 6 and 6 Plus, however, they're only 0.01 inches wider, taller, and thicker. This slight increase should not affect cases, and you should be able to use your iPhone 6 or 6 Plus case with the new s-devices.
Also, can you put an iPhone 6s screen on a 6?
NO. The internals are different and may not fit exactly but the external shell is identical and has the exact same design. If you buy repair parts, just make sure it's compatible. If you want to see what both phones look like on the inside, go on YouTube or ifixit and watch people open it and take it apart.
Are iPhone 6 plus and 7 plus screens the same?
Apple opted to carryover the same general design from iPhone 6/s to iPhone 7/Plus, but a few key changes break forward compatibility for the majority of previous generation accessories. The width variance is much more significant on 7 Plus so you'll almost certainly need to buy a new screen protector.
