Spelling for a post-proto-modern experience

I can’t decide how to spell this thing; I really can’t. US or British English? Double or single quotes? What the hell do you do with a book that doesn’t take place in either place written by a more or less American type guy living in Britain?

This spelling bit has been a nagging question all throughout the writing and creation of The Gates of Vienna, namely because the novel/story/world is all about place and the movement, creation and dissolution of place. There are lots of places, like various duchies, empires and even cities that now have different names or are now in places that are now independent countries.

So what has been the solution? Do all of it. Mix it up. To do the proper Baroque or rather proto-modern solution which is not to be bothered about all the categorisation and drawing of hardline in understanding the world.