Kryoanut is intended for extreme sub-zero temperatures. It is not intended as a long term installation. That said, doesn't seem to do too badly for a year or two. Not had any issues with my 7700k and I repasted that under the heat spreader about 5 years ago. My GPU also has kryonaut on it, but that installation is still pretty new.
Thermal Grizzly Hydronaut is probably preferred if you don't plan on touching it for a while.
As for thermal pads, I've always used Fujipoly and whatever EK ships with their stuff, also some old Arctic pads (which look an awful lot like the ones from EK). Gelid doesn't seem to like to talk much about their pads specifications, but the one chart they show shows a 6% improvement in temperature over a 5 W/mK pad. Fujipoly rates theirs at 6 W/mK.
But they are right that it does depend on the thickness and application, so actually results outside of a lab will vary.