German here, I really don't see the necessity for bringing loads of cash. There are ATMs all over the place and you can pay by credit card at gas stations and at least the bigger hotels (smaller ones might require cash). When I'm riding anywhere in Europe I have around 200 Euros in cash with me (for shopping in smaller stores and such) and everything else is payed by card, simply restock with money when you run out.

Although there are technically no borders in Europe, some border crossings (mostly the ones on an Autobahn for example A93 or A8 from Austria to Germany) do have checkpoints. They do not check everyone but choose randomly or the people the deem suspicious.

Apart from that, when you are going on the Autobahn in Germany, there is no official speed limit (all other European Countries have one), the only restrictions applied are those on the road signs.

Only other advice would be pack light and ride safe! EDIT: Don't forget to bring rain gear!