Not quite the same but I've just taken off some Gravel King SKs 700x38c (measured 40c) and replaced with Teravail Ramparts in 700x38c (measure 36c). Different tyres but the ramparts were much nicer to setup tubeless and are much nicer to ride (could be placebo).
I don't know the Ramparts but the fact that GK SKs are a bit of a pain to setup, to me, implies quite a supple tyre which "normally" equates to faster. But then you obviously have tread impact and stuff so this is a bit of a fluffy opinion.
GKs are more supple than ramparts. Tubeless Ive struggled to move on from the GKs. Easily get 6/7 k Kms out of a set.
I've some wonky 38mm ramparts you can have for nothing if you like?
Not quite the same but I've just taken off some Gravel King SKs 700x38c (measured 40c) and replaced with Teravail Ramparts in 700x38c (measure 36c). Different tyres but the ramparts were much nicer to setup tubeless and are much nicer to ride (could be placebo).