I'm assuming akame ga kill powerscaling is higher, correct?

No, but only a few characters in Demon Slayer outscale Akame ga Kill. E.g. Muzan, Yoriichi, maybe some of the Hashira.

Rui is immortal and his treads are limitless while Lubbock can run out.

Which verse does Esdeath belong to?

Akame Ga Kill