I like 75/25 ground chuck.
I grill on a weber until medium rare with salt & pepper.
I find the 25 percent fat makes a moist and juicy and tasty burger.
Just made them last nite and had one with american, both sides of the bun have cheese, and one with an artisanal cheddar.
They were some of the juiciest best burgers I’ve had since the last time I did some grillin.