I was surprised how slow (and noisy) the GK SK 650Bx48 was compared to the 40mm Rambles or G-Ones. I don't think the thinner versions are that slow (although maybe the size exacerbates the problem).
yes, the SK buzzes on pavement. I have no issues with how it rolls. Not slow on unpaved surfaces. My (narrower, not “thinner”) 42mm slicks are quicker on pavement, but not a big deal for me on mixed, mostly unpaved rides. I have used “road” tires that are slugs be comparison.