iPhone X/8 (Universal Template)
As a big fan of automatization an every process that can be automated, I made a custom template for designing both for iPhone X and iPhone 8 Plus on one artboard. It's not perfect, and it depends on the situation, but it suits well for fast prototyping for both screen sizes at once. The trick is in careful choosing of right options for resizing in Sketch inspector. Enjoy.
Download Template (.sketch)