Hi Carl,
There are several things to consider. 1 - Tuning the servos, 2 - homing the axis, 3 - squaring the machine and 4 (your question) - running the axis.

Some of this depends on your controller and some on wiring. To answer your question first, the drives should be wired in parallel to the controller so each drive receives the same step and direction signal at the same time. If your mechanics have the motors spinning in opposite directions you must reverse the direction input somewhere along the way, either in the drive with the reverse function, in the controller or in the encoder wiring. If your controller is capable you can actually use them as 2 separte axes (like X1 & X2) and tie them together in the controller.

Homing the axes, setting limit switches and squaring the machine will be more challanging. Once the machine is tuned and square you're all set, unless you lose power to the encoders, then the machine must be re-squared and homed. Since you'll likely tune the axis and square the machine with 2 computers this works OK when you build it, but not if you ship it and need to re-square it again at set-up.

All this can be done with 1 computer if you create a ring for the drives, but you'll still need to connect them to a scope for the tuning. They could possibly be connected to one hard scope on 2 different channels to allow tuning both at one time. When tuning them with 1 PC you'll have to make very small changes to the tuing files as you go back and forth. Torque will give you an idea which drive is working harder.

There is a ton more stuff we could cover, but some of it depends on how you plan to use the machine, how your controller works and if you're selling the machine to someone else.

Let me know how else I can help.
Victor