@Angelo 

I’m not sure that the seating plan is 100% true. Because the same seating plan style is also for the EC to Switzerland with the new Giruno trains, and they have windows at every seats, but at Trenitalia.com seat plan not. But this could be so, because it’s a swiss train. I hope they have a good seat plan for their own trains. 

NOTE: Frecciarossa trains do not run in the same direction. Sometimes is carriage 1 in the front next time is it at the end. You know where the carriage is only about 1 hour before departing at the first station of the train ride. So we can not tell you on wich side you should sit. 

I have compared the seat map of SEAT61 with the places you can choose on the Trenitalia website, and it is exactly the same.

What I would like to know :

On the seat map you see the seat numbers, thick lines and thin lines. What does the placement of the windows indicate? Are these the thick lines?

Okay, but do you know which side of the train is best for the best view, assuming carriage 1 is the first on the train, where the train driver sits?

Carriage 1 doesn´t mean that there the traindriver sits as many Italian Stations are “Kopfbahnhof in German” means the train departs in the same direction as it comes from. Means the driver have to change the driver cabins. For example the FreeciaRossa Turin - Reggio Calabria change 3times on the route the direction of travel in Milano Centrale in Roma Termini and in Napoli Centrale So sometimes carriage one 1 is at the front and sometimes at the end.

As trenitalia doesn´t know in which direction the trains will be (due delays they maybe didn´t stop at one of the station and the trainset is then in a different order) they doesn´t publish the train arrangement far in advance.

As said above it´s usually published 1hour before the depature of the train on it´s origin station.

@Angelo @seewulf 

I understand that it is not possible to say with 100% certainty what the composition of the train will be. In other words, whether coach number 1 will be at the start of the train, or at the end of the train.
So far this.

But what I wonder: When the Frecciarossa in Rome Termini leaves with coach number 1 at the beginning of the train, direction Milan Central.
Then it is possible to say which side of the train is best for you to take your seat, in order to have the best view?

Or am I completely misunderstanding it....

The most important thing for me remains which seats are nice at the window. Because that is not clear on the seat map of SEAT61 or Trenitalia.

I hope someone can help me with this, give me more clarity.

On Youtube there are some videos that shows, that most seats have a good position to the windows. 

Maybe you can see some seat number and choose them. 

Thank you @Angelo 

I'm going to look into it further.

I found even clearer information on the website
The man on the website also helped me a lot with my choice of seat.

In the end I chose coach 3, seats 5D and 6D.
So excited to see what it will be like!