For starters: try to google panchromatic, superpanchromatic, orthochromatic, orthopan and infrared....
Those film characteristics alone have an impact on the image / subject.
Next would be film speed, but I guess you were aware of that. Try shooting a smooth waterfall with long exposure on a bright, sunny summer day with ISO 400 or even 100. Unless you have a really dark ND filter with you, good luck exposing for several seconds. Pull processing won't help (enough) either.
You answered your own question - ND filters. And if you want orthochromatic film - go ahead and use it. I'm not saying it's wrong to use it. You can do a lot with filters to replicate that type of color rendition in panchromatic emulsions. Infrared - OK you win. It's still not difficult.
But, to get back to your questions:
I generally like smooth pictures with little visible grain, at least for my photography. Only in very few situations I like to have visible grain. That's why I got to use the combination of Acros + HRX3 so much. Produces very fine grain, yet a nice, sharp, crispy image.
Superpan (in RHS) on the other hand needs much longer processing. Way too long for me (and my patience/arms). In HRX3 it won't get a crisp as the Acros. I use HRX3 for TMY, too. Superpan, however, I only use when reverse processing.
So, you like as little grain as possible, while the picture is sharp and crispy. That's exactly what I get from Acros in replenished Xtol.
As an end note:
I am curious - why do you say that you don't believe in films being difficult (or good) in certain situations, when in the same sentence you exclude "specialty" and "document" films? To me, that's a contradiction and proves that films in fact have different characteristics. Document or "specialty" films, of course, are extremes. But why - in your logic - would different characteristics not exist for all other films then? Why would a single manufacturer produce various films with the same speed if they all can handle the same situations and even achieve the same look when processed longer/shorter (or agitated more/less often) like you suggest?
I use mainly two emulsions, Acros and TMY-2. They do everything I want them to do, and then some. I don't have to look elsewhere to get the results I want. I don't care about the plethora of films out there, because changing to a different emulsion doesn't make the pictures better for me. I have tried lots of films in the past, infrared from Kodak and Konica, Tri-X, FP4+, Ilford Delta 100/400/3200, TMax 100 and 400, Plus-X, Foma 100/200/400, HP5+, Pan-F+, Neopan 1600/400/Acros, ORWO, Efke 25/50/100, Agfa APX 100/400... I have pretty much tried most of them. But when I settled for one major emulsion, put on my blind-folds, and just learned how to treat that one emulsion, all of a sudden the quality of my work started going up, because I fully learned how to exploit that single emulsion to the maximum. I can handle night time shooting, extreme contrast, low contrast - any lighting situation by just changing how I expose and process the film, and yield negatives that print easily at Grade 2-3.5 with results that I am more than happy with. I don't even have to think about exposure and development. It is automatic. I can instead focus on the content, the light, expressions, composition, gesture... the important stuff. Film and developing film is just a means to an end, it's a tool. Put too many tools in the tool box, and you'll be thinking about the tools too much. That's my opinion.
The bottom line is that I don't need a film with specific characteristics to get me what I want and need. I get there with technique and a dollop of critical thinking about what's truly necessary.
The addition of one more emulsion to my line-up is so that I have a recourse if the other were to be discontinued; I'm covering my own rear end.
