Smooth side for pastes, you always strop on the smooth side.
Good chrome oxide will be a powder or paste without big hard lumps, Grading it can be hard so people tend to buy it from reputable vendors like SRD. 0.5 micron is the general banded about grit rating so somewhere near 15K perhaps higher on the best stuff, and a lot lower on the cheap stuff. It's an abrasive green pigment used in paints ect so it's rarely sold with a grit rating as we are not the main market for it.
Chrome oxide crayons can be hit or miss. The razor branded ones tend to be well graded, but polishing graded sticks are often laced with other abrasives like Alu oxide that speed them up but make them unsuitable for razors.
Shave ready doesn't mean they actually did anything to the edge. There is a trend with sellers to put that phrase on the product and not hone them up. If like you say your 6K edge was sharper, then your blades were not honed to a satisfactory level. Send one out, It'll come back almost as sharp as the shavette you have. You can also try a hanging hair test to see if your blades pass.