I have been trying to find the best Ethernet controller and break out board that works with Mach 4.

I have tried UC300Eth and ESS smooth stepper and have found they are very difficult to setup and keep running.  Any changes they crash.

I am running a simple 3 axis machine for wood routing.

We use the ESS and PMDX-126.
The PMDX just takes 120 or 220 AC power and provides the power for the ESS which mounts on it with some standoffs.