Hi and welcome to the forum!

I like your project, the setting definitely makes for an interesting one.

I think with the map you were on a good path with the one you posted. The projection seems good for a board game. The one off wikimedia is a straight top down view, and although it shows all of Europe, I don't think the parts east of what now is Germany are needed for the game. As far as I remember, most of the wars happened in western Europe. Not entirely sure though...

Anyway, my point is, if you want enough space on the board for markers and such, you'd need a proper projection, since most of Europe is relatively small.

I also wouldn't worry about the coastlines too much, realism probably wouldjust get in the way of praticalitiy. If you look at the boards of Ticket To Ride, for example, they are nowhere near accurate.

GIMP s not a vector editor, it's pixel based. Illustrator or Inkscape (which to my knowledge is freeware) are vector based programs.

I don't think I could help you with the actual drawing, since I am still learning and have limited time, but if I can help with anything else, I'd be happy to do so! Looking forward to seeing how this'll turn out!