It's a texture replacer, but this distinction doesn't matter if you're using BAIN to install, configure and uninstall you mods.
...
edit: When not using BAIN, installation order does matter a great deal, yes. Not so, when using the best tool for the task. More to the point, you can rectify any installation order issues with the greatest of ease, in BAIN, whereas without it, it's likely to be a nightmarish undertaking... at best.
Respectfully, I have to disagree a bit on these points. While BAIN makes it much easier to manage the install order, the order you install files
does still matter. In the case of conflicts, the latter, higher numbered install file (lower on the screen) still wins. Particularly in the case of textures and meshes, replacers are overwriting specific files in existing paths. (If they are going into their own unique folders then they are not 'replacing' anything.) So, the last installed file wins, always. "There can be only one."
As for the OP's questions: the above considerations should govern your decisions. Those categories are an aid to help you group mods that make similar types of changes together, so you can then more easily decide which should win in the case of direct conflicts. Therefore many of those choices are discretionary. BAIN shows you (in the upper right-hand portion of the display) how many files from other mods conflict the currently selected one (under the 'General' tab), and exactly which files are conflicting from which particular mod (under the 'Conflicts' tab). That helps you decide if you need to re-order or re-categorize your mods. It all depends upon which mods you want to win. (Don't forget to 'Anneal' after changing the install order.)
(BTW: when looking to identify which files are 'missing', look under
both the 'missing' and the 'mismatched' tabs. They are totaled together on the 'General' tab.)
Personally, my responses to those decisions would be: (I based on the IO categories at http://tescosi.com/wiki/A_General_Order_for_Installing_Mods.)
1) "Exterior/Dungeon Actors Have Torches": 05 Gameplay Changes and Tweaks.
2) "Koldorn's LOD Noise Replacer": 11 Large Mesh Replacers.
3) "Streamline": 02 Utilities.
4) Crowded Cities/Roads: 09 Companions and NPCs. (Primarily because too many NPCs in an area can cause FPS hits, so that's what I want to look for to disable when testing it's impact. But '16 City & World Aesthetics' is a possibility as well.)
But there is plenty of room for disagreement, and perfectly compatible placement in other categories.
As you can see, there is no reason you can't create your own categories and sub-categories. I number mine so they sort properly and help me tell which category will override the lower numbered ones. I have 23 major categories and more than that in sub-categories (mostly 'pre-' and 'post-' certain significant mods), but that's just to help me make decisions.
And, anticipating another question, I tend to simply place mods within a category in alphabetical order unless there is a need otherwise (such as a conflict winner preference). In practice, I don't have many conflicts within a category ... outside of replacers.
-Dubious-