Two questions about German folk metal...

I have learned of a type of folk metal out of Germany.

They use a type of medieval German bagpipes and this genre has a lot of medieval influence. Here and Here are good shots of the pipes (scroll down past the band logo on the second).

Here are a couple of examples of the bands:
*Tanswut *Nachtgeschrei *Subway to Sally *In Extremo

I enjoy figuring out when various nation’s folk is being incorporated in its music (like Trollhammer, Metsatoll, Lordi incorporating it in one video, etc).

If anyone is familiar with this genre, do you know if it, or various bands from the genre, has basis in medieval German folklore? If you know any of this genre that use the style of the German folk band, please let me know?

A second question: is German folk in any way related to Celtic folk? The bagpipes these groups use sound very similar to Scottish Highland pipes. I know that a couple of these bands cover old Scottish traditional songs.