The KLR would be my choice of the three listed but it's a bit of a moot point if there's none for sale in Germany. If you are, as you say, tall, skinny and inexperienced then I'd suggest as light a bike as possible and a 250 trail bike would be a great choice. Others have listed the possibilities and any of them would work.

A few points to consider though:

Don't dismiss the advantages of light weight and get seduced by power output and engine size. On anything but Euro motorways / trunk roads you'll rarely need more than about 30bhp.

Reliability is paramount, and especially so if grease under the fingernails hasn't featured much in your past. You can forgive a bike a lot if it starts ups and moves under its own power when you're in the middle of nowhere. IMHO and your circumstances stay away from anything that doesn't have its parentage somewhere in Japan.

Once out of Europe you'll bless the day you chose something with decent suspension. Small trailies (or big ones come to that) are not generally blessed with all day comfortable seats but at least the suspension eases the pain when you hit a pothole. Aftermarket "fixes" / reupholsters litter the internet but believe me when I say that your posterior does (eventually) adapt.

If you think choosing the bike is tricky, just wait till you start dealing with the paperwork!

Good luck though, it sounds like a great trip.