Because we were talking about Adams and Eggleston, my comments are meant about art photography not photography in general and certainly not photojournalism. Sorry for the lack of clarity.

Photography does not rely upon processes such as PP but rather ideas. Photography being free from much of the material, technical and labor demands of other media focuses solely on concept. Contemporary photography is about concept and information more than aesthetic concerns.

Explain what you mean by real subjects. What would be a fake subject then?

Sounds like you are essentially talking about Ansel Adams vs William Eggleston.

The Kodak used the early form of roll film which was paper. The emulsion after being developed by people at Eastman was then transfered to glass plates for printing of the positive. The camera was shipped back to customer preloaded with film. Eventually cellulose nitrate replaced the paper. I'm not sure when the Kodak cameras switched from round images to rectangular.

Prints weren't always rectangular or square.

https://mashable.com/2016/01/09/early-candid-photography/#h3ESj8mATaqM

Print size and viewing distance are highly subjective and depend on the meaning being expressed in the photograph and how the photographer wants the viewer to experience it.

For instance: This series is printed 5.5" x 6.5" with the actual contact print size being 4"x5" http://www.kristofferjohnsonfoto.com/work/#/vanished-expressions/

I tried printing it larger but the images fell apart conceptually and lacked the same visual interest and experience. The smallness of the images forces the viewer to be intimate with the prints when viewing them because they have to get close.

The work of Andreas Gursky is also highly dependent upon print size. His prints are massive. If they were not as big the impact would change dramatically. https://www.guggenheim.org/artwork/artist/Andreas-Gursky

Viewing distance can be integral to ones images. Mark Rothko's large color field paintings may seem empty to many but they are likely standing to far away. Rothko in his writings suggested that the paintings be viewed closely, 18" or so. Standing so close to these large color fields gives the viewer the experience of being absorbed by the color and enjoying the very subtle transitions within the field.

https://www.moma.org/learn/moma_learning/themes/abstract-expressionism/the-sublime-and-the-spiritual

I wouldn't base much on a Wikipedia page. There are far more reliable sources.
For instance: http://www.dhw-fototechnik.de/en/rolleiflex-slr/rolleiflex-hy6.html

To my knowledge the Hy6, like most medium format cameras can use a film back or a digital back. It is likely though unlike the other older cameras that came before it, this camera was designed to be used with a digital back from the start.

I really like it but I would suggest burning in the left edge right below the upper corner a bit. Otherwise it is a fantastic image

Also, here is a book that may be of some help. https://www.abebooks.com/book-search/title/manual-close-up-photography/author/lester-lefkowitz/

You may also want to try backlighting the paper

There is always an f/stop but it sounds like it is fixed and cannot be changed. You mention the focal length as 160mm. What kind of focus is expected to be achieved at 160mm with this sort of lens? Essentially, is 160mm of bellows required for focusing at 1:1 or some other ratio? The amount of bellows required for a lens at infinity is the same as the focal length but I suspect this would not be true for this lens since it is specifically for macro work. How are you focusing?

I would suggest doing a test with an object with more contrast and also using more light to do the test. What was your f/stop and shutter speed?

What do mean by best? This is dependent upon what the scene and photographers vision requires.

Also, at this point posting a photo will not result in the topic being moved to the gallery
Do you have a website where your work is displayed? If yes, can you post a link to it?

The cropped digital sensor size is based on the Advanced Photo System film standard that was introduced in the 1990s. It was developed as a joint effort by Kodak, Agfa, Fuji and Konica. My understanding is that it was a colossal failure however, the standard sizing has remained. This is why Canon refers to their crop sensors as APS-C.

Diffraction certainly impacts image sharpness at smaller f/stops. My point is that it shouldn't matter because absolute sharpness is overrated and insignificant.