Search:

You are simply modifying the base stone's qualities. You can't say a Shoubu edge is a Nakayama edge but to confuse further, Nakayama quarry is situated in Shoubudani mountain :)
FWIW both...

Oozuku Asagi are known razor quality finishers. Takashima not so much & hard Karasu not so common. Again ask the seller, if you trust him.

The numbers are relative also. I bought a 5+ stone...

Yes & no. Soft stones release grit more readily & are rarely as fine as a good hard razor stone, tho some expensive ones come so close there can be overlap. The tendency is to slightly less sharp...

Depends on your price limit.
The most affordable yet dense layer is Namito. Asagi & Kiita colours will be neighbours there.
Travelling higher up towards Aisa & Tomae, ie less dense should be...