The Eurail Pass covers trains (+ boats on Lake Thun and Brienz). You get 25-50% discounts on boats and mountain railways in Switzerland.

If you buy a Swiss Travel Pass (quite convenient I agree) it is only valid in Switzerland. You'd need a regular ticket from Paris to Basel on sncf-connect.com + tickets in Italy.

Since high-speed trains are very expensive last-minute I'd recommend the Eurail Pass including in Switzerland + separate tickets for boats (see discounts above), buses or trams in Switzerland. High-speed trains in France and Italy require seat reservations. More info here :

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

https://www.seat61.com/interrail-and-eurail-reservations.htm

For Paris - Basel : either 29€ for the direct train or 10-20€ for a TGV to Strasbourg or Mulhouse.

Do not wait to book high-speed trains since they can sell out.

Thanks for the information. 

If I have Eurail pass and reserve the high speed train seats in advance, can I reschedule the time without any extra charges?

… Wrong topic, forget what I typed here….

Seat reservations are generally not refundable nor exchangeable. However availability on the day itself or the day before is not an issue in Italy with lots of frequent trains (every 15 min between Rome and Florence for example).

But for a big journey like Rome/Italy - Paris I'd recommend buying right now. It is still peak season after all.

Seat reservations are not a thing in Switzerland so you've got full flexibility.

Hi,

I am buying a Swiss Travel Pass for my stay at Switzerland. I have two questions regarding my travel for France-Switzerland & Switzerland-Italy:

1. If I am coming from Paris to Basel, which train should I book? Does Swiss pass start from French border city to connect to Basel? 
2. If I will go to Venice (Italy) from Basel, which train should I book? Is Swiss pass valid until any Swiss-Italy border city on the way to Venice. I am also planning to buy Italy Eurail unlimited pass. 

Basel SBB is the border point coming from France, search tickets to there on sncf-connect.com

To Venice : well it depends which route you take but either Domodossola or Chiasso

I'm not sure that Italy One-country pass is good value since you need to add a 13€ seat reservation for every Frecciarossa train anyway.

Are you sure that a Global Pass doesn't make more sense ? I'm pretty sure that it is the best deal (in addition to a few cable car tickets -> discount with Eurail) for your very limited time. Otherwise for Milan - Paris on 28th August expect to pay 150€ per person.