Both @Wyvern and @DaltonSpence raises some interesting points about scaling here, and the critique of scaling in a map.

Personally for me, (A)D&D (and several others) have always been about a medieval setting with a twist. The introduction of magic and adventurers change the picture somewhat, but for me, these people have always been a kind of privileged people. Not everyone is a magic user, or even know a magic user. A town may have a town church with a few clerics and a town mage, but these few people doesn't significantly change the town outside their own abode, they have their own things to worry about, and their services are expensive enough that the average peasant/shopkeeper/innkeeper/smith/hunter/etc can't afford their services just to make simple things easier (like building a house that defy the general medieval technology level). Adventurers find treasure and bring in money, but while it may make the adventurers rich, it isn't that much divided over a town, making their contribution minor as well. As such, I've always felt that anything not adhering to medieval standards is "wrong" unless there is very good reason for it (and not all innkeepers can be ex-adventures who retired with both fortune and magic). And thus I've felt that a lot of the buildings from official sources are just plain wrong, either just because they are more focused on working as a battlemap than being a true building floorplan, or because the original designer was just ignorant of the subject matter. It just feels wrong when a common single-bed room at a common inn is larger than many people's living rooms in modern times.

Of course, many people will disagree with me here, one told me years ago that he didn't see anything medieval in D&D at all. Some people think I am horrible boring, and think it is much better when the world is filled to the brim with the fantastical. This is of course a matter of opinion. I find that I have more fun when the fantastical is rare, and the world itself is "as medieval as possible" within a realm that after all do have magic users and dragons. But the fact that I prefer one style doesn't make the other viewpoint less valid. Whether you made the map because that's the way you like it, or because you're trying to stay true to the source material doesn't matter. If you end up with what you were trying to do, then it is a good map.

OK, that turned out to be a longer rant than expected. What I was trying to say is that I find these aspects of critique both interesting and valuable. Not just for the actual mapper, @Dak in this case, but also for others in thinking about how your map should look. Some critique may or may not be invalid for the current mapper, but are still valid points to make in a more general sense.

It's usefull when you want a set of shades from a different base color than the ones from the default palette.

You can change the default wall to be whatever you want. The :DD2WALL: button just starts the drawing tool named Wall, Default. You can edit this to change the properties (advisable to make a copy of it first to preserve the original, but if you want to edit the tool that is used by the button, you of course have to edit the original, and just keep a copy under a different name as a backup). To make it cutable, all that is required is that it is on the WALLS layer. From your images, you are using SS4, and I don't seem to have a problem with doors cutting that wall though.

To make them into single walls, you need to do some manual work. Erase the entire wall (one of them) where there is a complete overlap, and use tools like :CC2BREAK: to split and cut parts out of walls where you have a partial overlap and don't want to delete the whole length of the wall.

In addition to what Sue is writing above, check for double walls. When I look at the screenshots you post, the door is clearly cutting something, otherwise there wouldn't be a white rectangle there. And the wall fill pattern in the second image is offset from the first one, indicating that there seem to be two walls on top of each other there. (The wall cutting functionality only cuts one entity)

I think you may be looking in the wrong place for the files. FilterTest2.dll is found in the Filters directory inside the data directory (C:\ProgramData\Profantasy\CC3Plus\Filters), but this is not where the actual dll's reside (unsure why that test dll is there at all). The actual dll files are inside the Filters subdir in the CC3+ installation directory (C:\Program Files (x86)\ProFantasy\CC3Plus\Filters) (and there is no FilterTest2.dll there).

Try creating a new map and see if there is any difference.