GeneratePress 100000%, but buy it. Don't be cheap. It is worth the money.
Their support will answer in 20 mins even if the question is not related to the theme, but to other issues - like plugins (that they didn't made), they'll make custom CSS for you, and explain everything to you like you never ever seen WP. I'm not affiliated with them (well, not here, I'm their affiliate).
We're using it on over 400 sites for kinda "complicated" things, and over 300 for basic (yep, over 700 sites in total).
"Complicated" = required custom work, "basic" - imported from site library and customized.
One of those "complicated" gets over 7 mil visits/months (sorry for bragging, I'm just proud), but we do have a custom server/hosting and dedicated team that manages it.