A cycle path has largely been laid out on the eastern side of the lake. The idea behind it is very good - because the main road is sometimes very busy. However, the pavement is partly damaged and the path is interrupted from time to time due to work. Well suited for slower tours, as a racing cyclist I would still recommend the road if necessary.
Lake Iseo has nothing to envy the Como or Garda lakes.
Great 60 km loop around the lake, all flat.
I'd suggest you to take the beautiful Bike path Ciclabile Toline-Vello, starting from the village of Pisogne.
In August and during the sunny weekends be cautious as it is shared with pedestrians.