Use vertical rhythm in Pages.app and anything else that doesn't have a grid built in.
Simple macOS app that displays as an overlay atop your other windows. It prints a repeating series of horizontal lines. The distance between lines can be customised.
The app can be downloaded in a zipped archive at https://github.com/bygri/VerticalRhythm/releases/download/1.0.1/VerticalRhythm.zip.
The pre-Sierra version is at https://github.com/bygri/VerticalRhythm/releases/download/1.0.0/VerticalRhythm.zip
That's all.