What coarseness of japanese waterstones is ideal for cooking?
Oh absolutely, you certainly don't want to sharpen a kitchen knife on a 200 grit stone! You'll want one medium stone in case you ever need to remove a nick or something (but then you should probably take your knife to a pro at that point), and then probably like 2000-4000-6000 grits for routine polishing. (Note Japanese grit numbers are different than American oil stones).