Sixt - First Europe Rental - Cancellation Policies?

My wife and I are considering renting a car to drive from Switzerland to Germany and it's our first time renting in Europe so we're curious about the whole process. Right now we're wondering what the cancellation policies are for a pay at location (not pay in advance) rate with Sixt? I'd like to get a confirmed quote for the trip but just in case our plans change, want to make sure I can cancel it several days + in advance.

you can basically cancel 1second before your rental should start.

but oneway fee from switzerland to germany won't be cheap.
better rent in Germany, go to switzerland and back to Germany.