Here we could see the size difference in iPHone X actual screen size.
I know it has wedge on top of the screen .. so am I safe to assume to App size occupied by app in iPhone X and iPhone 8 plus is same.
Can somebody clarify
Actually Screen size and resolutions both are different for iPhone 8 Plus and iPhone X.
But there's no issue with apps running in both devices, You have to remember only one thing is, "Safe Area". Just keep it enable, so that your top and bottom contents of the app becomes proper for every devices.
For more information you can check below reference
https://developer.apple.com/ios/human-interface-guidelines/overview/iphone-x/