Most documentation is available here (use the check box to limit to the TX1):
This requires a separate login and registration to download most docs…forum login is insufficient. You could then put “carrier” in the search box.
Generally speaking much of the I/O is 3.3V, some is 1.8V, and there is a jumper to select 1.8V or 3.3V on some of the I/O (default is 3.3V for the jumper position the carrier board ships with). I’m not sure if there is a rail suitable for powering an external device if that device consumes any significant current…you’d have to be more specific if you are talking about powering the device instead of I/O voltages.