I have not come across house museums in Venice. However, of all the large palazzos that are open to the public, Ca d'Oro gave me a little feel for what life might have been like with a view on the Grand Canal... particularly the balcony and the courtyard.
Also, while I really don't like modern art, I found the Guggenheim to provide an interesting little glimpse of the life of Peggy Guggenheim. The day I visited, I also enjoyed the patio area on the Grand Canal – the day I was there it wasn't at all crowded. That may be atypical. But the home, as well as the art, are definitely 20th century style, even though the building is much earlier.
Finally, the secret itineraries tour of the Doges palace will take you up into the prison cells under the roof – if you want a different feel for what "Home" might have been like for some unfortunates.
If you were going to Florence, definitely go to Palazzo Davenzati. It is a wonderfully restored/furnished home of a late medieval/early Renaissance successful merchant family.
Edit: A wonderful way to experience Venice and surrounding islands is to just get on a random vaporetto and get off somewhere that looks interesting. But if you were getting off at a very small or less-visited islands, make sure you know the schedule for the last boat back (and for some of those islands, the boat stops only on request). Getting a vaporetto pass makes this type of exploration affordable.