Omio reservation screen
I forgot to post something, so I thought I'd mention bus/train reservations in an additional post.
Just like with ferries, I had no experience in making reservations for buses or trains, so it was a matter of trial and error.
The first reservation site I found was Omio. It covers a wide range of Europe and has a wide range of transportation options including trains, buses, and planes.
Actual bus companies include Flixbus and Alsabus (Flixbus doesn't run much in Spain), and Marinobus night buses from Rome to Bari.
Naturally, there is a fee charged by the reservation site, but while I was making various reservations, I looked into whether it was possible to book directly with the bus company that operates the bus, and found out that it was possible without a reservation fee.
Also, at first I didn't know what to do and the screen displayed yen when making payments, so I made the reservation as is, but it turned out that it was actually a little cheaper to pay in euros, so from then on I decided to pay in euros.
The same goes for trains, and at first I used Omio to make reservations, but along the way I found out that there was a reservation site called Trainline, so I started using them depending on the route.
Omio allows you to make a wide range of reservations, so it has many benefits, but there are strong and weak routes, so I think one way to use it is to use it accordingly.