There's really very little difference between Scottish and English broadsides of the period. More difference in "educated" writing, as English was moving to a standardised grammar and spelling system (but only for official and literary purposes; normal usage in the North of England, for instance, still confuses foreigners; they always seem to think that it must be Scottish if it has words like "bairn" and "lass" in it).

At the same time, Scottish writers were re-inventing their own regional form of English as "Scots" or "Lallans", or whatever you like. Scots hasn't really developed a standardised spelling system to this day, though you'll always come across people who think that certain forms are more "pure" or "Scottish" than others.

17th and 18th century demotic English is just as much a foreign language as Scots of the same period, really. The difference is that people think that "English" is easily modernised and "Scots" isn't. As I said, I prefer to leave both well alone and just gloss difficult words if necessary. The result is less subjective and more reliable, search engines notwithstanding.