These are three separate trips, each with six nights and its own daily plan. Pick the places you want to spend time in; arrival and departure count toward the seven days.
Option 1
Rome & Florence
Ancient history and Renaissance art
Stay
Rome 3 nights · Florence 3 nights
Hotels
Two bases · One hotel change
Travel
Day 4: train from Rome to Florence, with luggage. Allow time for checkout, both station transfers and check-in. Rome–Florence trains
Leave out
Venice, the coast and a countryside stay
Choose this if the Colosseum, Vatican Museums and Uffizi are the reason you are coming.
Plan arrival in Rome and departure from Florence; returning to Rome adds another journey.
Day 4: a return trip to Modena. The Casa Giusti visit needs a separate transfer outside the centre; leave luggage in Bologna. Casa Giusti location and visits
Leave out
Rome and Florence’s major sights and a coastal stay
Choose this if you would rather learn to make pasta and spend time over meals than move hotels.
Keep the Modena day trip between arrival and departure, with the same hotel throughout.
Check flights, the month you are travelling and museum closure days before fixing the hotel order. Seven days includes getting there and leaving; it does not mean seven full sightseeing days.