We are doing Venice to Florence by train, then renting a car for a week to Siena and Tuscany. Then returning the car to Florence but we will be staying for 4 nights there afterwards. We can afford to wait for the train to Milan. But I could definitely book the train from Venice to Florence and then reserve a car around around train arrival time because our next night is spent in Siena (by car) (at Palazzo Ravizza, thanks to ChristineH for the recommendation as well!)
Tod, I get from your post that you would rent the car from the airport instead of the SMN station ? I have read all about it here and the really thorough explanations of Roberto as well. We'll have eSIM card too and I would say I'm not a bad driver in general. But yet, your comment makes me think. Would you rather arrive at the SMN station, then tram to the airport to rent a car or rent it directly at the train station or around it (as Borgo Ognissanti for example) ?
I guess it is better to book the car in advance ? That is the main point of my initial question actually. And since I need to know my arrival time to book the car rental approximatively, it makes sense to reserve this train in advance, then later on, when the schedule will be out, the one for Milan.