The old town is compact enough to cover entirely on foot. The Reichsstraße, Heilig-Kreuz-Kirche, the Käthe-Kruse museum, and the Danube promenade can all be reached within a ten-minute walk of each other, and there is no practical reason to use any other transport within town.
The train station is about fifteen minutes on foot from the Reichsstraße, which is manageable with a normal travel bag. There is a bus network serving the wider municipality, but visitors staying in the centre will not need it.
For day trips to Harburg, a car is the most convenient option — the castle is set above the village and not well served by public transport. Augsburg and Nördlingen are both on the same rail line and easily reached without a car.