None of this is hard to do by ferry, so I don't see much advantage to the tour, especially the cheaper one with no admissions to things. It's not clear how much commentary they make (I haven't done the tour). If you want to visit Bellagio, you'd have to confirm whether the boat would leave you there, otherwise you may be back at Varenna in 2.5 hours and looking for something to do. If taking a ferry to Lenno, you can walk to Villa Balbianello, but the small boat would bring you closer to that visit. If you choose the "George" tour, then that does take you past the limits of the popular mid-lake all-day ferry ticket, which ends at Lenno on the south end, but it's also possible to buy regular ferry tickets.