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And also there are cases where a 320 grit would be handy... ;O

The 4K with slurry cuts steel rather good.
I must confess to using a fine grit Norton India stone
on some problem razors to pull...

My bet is for #2.
The Norton 4k/8K is a work horse and
with a DMT the surfaces are going to have the
same degree flatness which is key.

Be gentle with the DMT and your 12k Cnat.
The Cnat will...