The output of inxi -Gxx should reveal which drivers are currently in use for the individual graphic APIs such as EGL, OpenGL and Vulkan. Sadly the output of lspci -vnn which you’ve linked doesn’t contain this information.
Additionally, I can’t really tell how you installed OpenTTD, in case you didn’t new, it’s available via to official [extra] repository of Arch and could be installed via pacman.
Furthermore, my suspicion is that you eventually missed some other package, especially one of the lib32 packages in relation to the nvidia drivers. Check this thread for guidance. If that won’t help, and to rule out other issues which are not graphics related, the output of inxi -Fxxc0z would also be helpful to diagnose the issue you’re describing.