For dpi, I try to find some golden fleece of nativeness and 1:1. For sens also. No accel. Typically means around 1600.
Back in the old days of 800*600 and 1024*768, I used extremely high sensitivities and accel, which essentially means I wasn't even moving the mouse around, I was only shifting my hand just a little on it. And that was great and much mourned. Obviously can't replicate it in FHD, let alone 4K, nobody has that amount of precision in his hands.