Thickness behind the edge is not a concern on sujihiki. Since you'll be slicing fish, not carrots, wedging is a non issue.
Richmond brand has two different manufacturers. The word on the street is the ones made in the US by Lamson have quality control problems on their heat treat. The ones made in Japan are probably okay for this purpose. The richmond Laser line and a few others are made in japan.
If you can wait like two weeks for shipping and can deal with the engrish on Rakuten, there are some deals to be had on better brands.
In particular, the misonos are cheaper than I've found on other sites.
carbon (but no dragon...)