The wiki article states that you should add the autologin line to /etc/pam.d/login, not to etc/pam.d/sddm.
If the login process is run by a PAM-based application, such as a display manager…then no further configuration is needed.
So, remove the line you added to etc/pam.d/sddm, and add it to /etc/pam.d/login instead.
Then reboot, open a TTY (CTRL + F3), and login. You should get a message that your next login will be saved. This means your next login to a TTY, not your login through SDDM.
This is to autologin to a TTY. If you want to autologin to your desktop using SDDM, that can be enabled through System Settings > Startup and Shutdown > Behavior.
I have never used an encrypted wallet, and I don’t have the time to research that for you, so I cannot advise you about anything on that.