Tinne,
We really enjoyed our hiking vacation in Tuscany. The overnight addresses were wonderful, from simple to very luxurious! The hikes were sometimes spicy, sometimes tough because of the altitude differences. As you said, without a GPS you can forget about this. Therefore, it is wise to mark the routes so you have a second check! Then, for the participants and especially the youth, there is also a kind of tracking! The route Landuccia - Guado was marked in a nice way, every few hundred meters a red/white mark.
Again, we really enjoyed ourselves, despite our getting lost adventure! You can also prevent this with marks! If you get lost, as we did, you can easily get into a dangerous situation where help is not readily available!
Many thanks on behalf of Winy and me and we wish you much success!
Greetings.