To add a bit on to what Wyvern said, note that a lot of programs, especially those online browser-based ones, do not allow you access to download the artwork, they only make it available for use within their own application. I don't know the specifics of each of the programs you mention, but it isn't unreasonable to expect they are not downloadable in a legal way, but as Wyvern said, you need to research each of them (or maybe someone here who uses them can comment)

Yea, Ralf only shows some simple editing there, but it gives a good overview of the process needed to manipulate hatch styles. But you can do any operation you want when editing them, including scaling them using the :CC2SCALE: command.

But yea, bitmaps are much easier to deal with.

The technique Ralf showed here unfortunately only works with bitmap fills. This covers most maps, but some maps, especially maps using line-work (like the landform maps) use different techniques for the fills.

It gets a bit more complicated to scale these. I am pretty sure Ralf showed that off in a video at some time too, but I don't remember which off the top of my head. I'll see if I can find a link for a video or something else, unless someone bets me to it.

If you try with for example the Mike Schley overland style, you'll find that this trick works the way Ralf showed it if you use it on a bitmap-filled polygon, like farmland for example.

edit: Ralf demonstrating editing hatch styles in here: https://www.youtube.com/live/-zZGWKT2pN4?si=LOm5YLc6CtJAds-j&t=1187

If you look at the prompt while using a mirrored polygon drawing tool, you'll notice that it offers you to hold down the control key to create smooth nodes. This allow you to create a plan that has both curves and straights in the same poly.

As Wyvern says, you can add pretty much what you want. The idea behind this project is that everyone can bring their own ideas to the table. A local map should obviously be consistent with the regional map it is taken from, but the general idea is to make it interesting by adding features and locations that wouldn't have been mapped at the greater zoom of the parent map. The marked city locations on the parent map are naturally going to be the largest cities in the region, but as you drill down to more close-up maps, smaller cities and other interesting locations will naturally start to appear. So make it yours, add your own lore to the area (if you want to), and make it an interesting place for subsequent mappers to pick for their maps.