ATMs

Generally, any bank affiliated ATM. Read the screens carefully to make sure there are no additional charges and never accept dynamic currency exchange offering to convert the Euro transaction to a Dollar transaction.

I've never been charged a fee for using Deutsche Bank ATMs, which are available at Frankfurt and Munich airports, and in towns, of course.

You might want to load a credit card onto ApplePay. I haven’t used more than €25 in cash so far on this trip.

If by rates you mean currency conversion rates, there is no difference, in Germany or anywhere in Europe, the network associated with your card handles that, for nearly all US cards it is about 1%, you may not even notice it.

There may be fees associated with using the ATM, but in Germany, I found many ATMs do not charge a use fee. If they do, it is 3 to 5 euros. If offered, proceed with the transaction in Euros, not USD.

I do suggest having some cash on hand, Germany, more than other countries it seems, still likes cash over cards. In main tourist areas, card use is common, but not unheard of to find a restaurant or shop that takes only cash.

Apparently the have some cash advice also applies to Austria if you're heading there.

Check if you have a correspondent bank in Germany associated with whatever bank you use. Deutsche Bank has a relationship with Bank of America, so I sought it out. Stay away from "ATM's" that just say 'Euros here', those will charge a fee. Seek out a bank ATM.

I was surprised how much cash came in handy in Germany. I used Apple Pay occasionally when I remembered. There’s more use for cash than I expected, smaller lunch places that only took cash, & churches had only cash for post cards, etc. Enjoy your trip!