I just finished the screenshot comparison site for the K1 release, using DarthParametrics suggestion of image sliders and a github repo. Thank you very much for that.
So if you're interested in seeing quite a lot of screenshots from the mod and compare them to the original vanilla look, just head over there: https://kexikus.github.io/HQSkyboxes_k1_Comparison/
The file size is pretty similar. The main K1 archive is slightly bigger than 200MB. Then there are of course the add-ons as well but those aren't that big either.
The TSL archive is quite a bit bigger. I think it's closer to 400MB or at least over 300MB.