Eileen,
Varenna is a quiet lakeside town & it's a nice place to relax & enjoy the scenery.
My mom & I stayed in Varenna 3 nights last fall at the end of our trip & we enjoyed taking the ferry & cruising the mid-lake.
We took the ferry to Bellagio one day but found everything to be expensive.
One day we took a bus to the city of Como & enjoyed visiting the Duomo, and it was here where we ate the best pizza on our trip at ' Locanda Barbarossa'
My mom & I also visited Lake Garda (day trip from Verona) & cruised the lower lake ( we purchased the day pass) & enjoyed exploring some of the beautiful lakeside villages (Bardolino, Garda & Lazise) We did not have a car, but if we did, we'd traveled to the northern part of the lake & would have explored Limone then taken the ferry across to Malcesine.
You may want to research the ferry website for Lakes Garda, Como & Maggiore here: http://www.navlaghi.it/eng/g_illago.html
You can read about the history, how to arrive there, what to visit & also check the ferry schedules on the website above.
If you've been to Lake Como in the past, & you will be traveling to Munich, I'd recommend exploring Lake Garda.
You could stay in the town of Peschiera del Garda then take ferry to visit the villages of your choice along the lake.