Sometimes these experiments lead back full circle. I tried HP5 and liked the look of the TRI X grain (little dots) better than the paisley looking smudged grain of HP5. HP5 looks LESS grainy though - Untill you are up close. Anyway - great shots are made on all kinds of combos every day.
I think the graphs are useful when you consider how you want to expose and develop a shot. If the film can record 10 stops and you have a 5 stop image, where you place those 5 stops, near the toe or near the shoulder will impact not only the contrast but the linearity of the contrast. More development time makes the graph steaper and less development time makes the graph flatter. I tend to stay in the middle of the graph if I can. (That is my level of craft at the moment) I have no fear of changing the slope however. I might opt to increase my development to make those 5 ranges expand the the whole range of the film (a portrait or still life?) - Or - more often, I will lower the slope (landscapes) with a short development time and know that I have captured details I had not considered. - Then I can print them up if I need to. The film speed changes with the change in the slope though.
Pyro and Catechol affect the shoulderof the slope. The tanning clamps the highlights by not letting fresh developer in after a certain amount of development has taken place. Metol based developers will cause less curve at the shoulder because they will permit more blocking in the highlights. It can almost seem like the highlights go out of focus due to the blocking.
One thing I am sure of - one can spend their photo time in technology and have no time to create or capture beauty. Technology is good but sometimes even the greats would just guess and wing it!
One last thing - grain and LF. I have shot TechPan, APX100 and TRI X in 4x5. The difference in the look of TechPan and TRI X is amazing. The Techpan is very very smooth and although you would not say the TRI X is grainy on a 16x20 print from a 4x5 negative, when you see them side by side - it is very apparent. Kind of like 8x10 contact prints I would guess. - Different when you compare -