Wow, that's a great first map. I hope you stick around the forum and make more maps.

Make sure that your line style is NOT set to 'Scale to fit ends' because that will actually do some undesirable scaling to the pattern to make a whole number of repeats for within the line. Once this is off, those issues should be mostly gone. Additionally, don't let your lines be scaled in 'paper scale', since that causes them to be different on export from what you see on screen.

CMB makes things into a single polygon, which cannot contain both smooth and straight elements, it has to be either a straight poly or a smooth one (I don't remember if CMB can work with smooth lines or not at all, but you can in any case convert the poly to smooth after finishing combining it.)

And no, you can't change the number of segments LTP creates unfortunately.

It depends.

But TRACED can be an excellent option here. You're probably ending up with a polygon that is easier to edit if using the "old way", since traced will need to place more nodes to approximate that rounding, and because TRACED runs on an image rendered from the entity, there can be artifacts like pixel steps. But you also often end up with a result that looks nicer.

Usually, the annuals come away the other way around. ProFantasy spots an artist already doing an interesting style (maybe as a result of a tip from the community), and then works with that artist to bring their style into CC3+ (as an annual or symbol set, assuming the artist is willing obviously). This basically means that the map types will reflect what the artist is already doing.