The other questions I have are do you use the common wire from each powermasters to connect to the Legacy base?
If you are using only the powermaster to each loop with its A and U, you can connect the 3 U's together and run 1 wire back to the legacy base. You can also connect the outside rails on each loop with a separate feed wire to the otber 2 feed wires and run 1 wire to the legacy base.
Also, do you connect both a an u wires from each powermaster to it’s own district or loop?
Yes, they are independent and each powermaster gets its own unique TR number which is 1 to 9. Reserve the TR 0 (zero) when you want to eliminate a Train you put together using tbe TR function.