I have been traveling on Italo and trenitalia. There are fares that cannot be changed, those that can be changed with fee but no refunds, and then flexible fares. italo has a fare where one can only carry baggage that goes under the seat in front (called smart fare). Thankfully for other fares there is still no baggage charge or seat reservation charge-- or anything like an overweight luggage charge. I could carry a baby elephant in my luggage and not be charged extra. Alas Italy does not recognize emotional support animals so said elephant would have to be in my baggage (with air holes of course).