In the future, I want to have it track on a single axis. I see no problem with this but, I have no knowledge of actuators.
Consider leaving your options open here. It's really not much extra work to add the second axis later, especially if you plan for it now, or at least make sure you don't do something that will ham-string yourself later
My set up is 12 volt and I've seen plenty of actuators but, I am not clear on the limit switch set up. Do I need one with built in switches? Should they be adjustable?
Limit switches are not necessarily required, but some form of limits is. Otherwise when your mount runs out of travel it will just bind up and bend/break something.
Option 1. Use internal limit switches, internal limit switches should be adjustable. This is the easiest.
Option 2. You can use external switches on your frame to cut the power to the motors when it comes to the end of it's travel. A little ingenuity required as you don't want to kill the power that will allow it to back off and go the other way or else it's just stuck there.
Option 3. Use some external control that drives the motors, but which is set up to only operate inside certain parameters. Arduino micro-controllers come to mind. This is the hardest of the three to implement.
PS Consider replacing the mount tube with a much longer one, it really makes it nice to mow around and / or work around. Mine is mounted with the pivot of the mount about head-high.
