Hello everyone

Is there anything else to do in order to bind protonvpv to tixati, except from choosing "proton0" in both "Local IPv4 and IPv6 address and interface"?

Is there a difference in choosing "10.2.0.2" instead of "proton0", and if which is the correct one?

PS: I did the test of downloading a Linux Mint torrent and the then disconnecting from the vpn while having the killswitch enabled, and the speeds dropped to zero.

You're doing it right. "proton0" is the preferred approach. If your internal 10.xxxx IP changes, proton0 setting will simply update to use the new IP.
If you specify 10.xxxx IP, then despite an active proton0 connection, Tixati will stop when IP changes to 10.yyyy.

If you had a generic name like "tun0" and used other VPN connections, I would've recommended strictly specifying the IP to avoid mix ups with different VPN connections.