Do we keep votes from puppet cities as Venice?
No, it does not; the City-State-provided votes are based on the number of City-State allies you have, and a puppeted former City-State is not an allied City-State. This can mean losing a vote, if you puppet a City-State you are already allied with, or it can mean depriving a rival of a vote, if you choose to puppet a City-State they are allied with.