The Taig mill has chromemoly 1/2"-20 leadscrews on X,Y,& Z however the are not acme.
Ball screws will cost almost as much as the entire Taig mill!
The CNC ready version has the motor couplers included, the are provided by Taig.
The Xylotec 4-axis kit is a bolt on to the CNC ready version of a Taig mill.
What are you going to be using the mill for?