For documents intended to be read on-screen, I've had very pleasant results with Merriweather, Merriweather Sans, and Cascadia Code (for monospacing). Mind you,

For documents intended to be read on-screen, I've had very pleasant results with Merriweather, Merriweather Sans, and Cascadia Code (for monospacing). Mind you, I use XeLaTeX or LuaLaTeX, which make using arbitrary fonts easy. My math text is still in Computer Modern; I still have to go look at various pairings to see what I like the best.