I'd double check with a multimeter, but I'm pretty sure the DCM should go to 0V (it's been a while since I've had to wire up a VFD!). Hopefully somebody else will confirm.

BOB wise, I'd guess the usual cheap generic 5-axis Chinese ones available on eBay is as good as any for a basic machine, as they include the needed circuitry to get a 0-10V analogue output for speed control. I'm not entirely sure if there is any difference between the green and blue ones...

PSU wise, I personally prefer DIN rail mounted supplies, but there are lots of options. I'd think you'll only need a 12V supply, as the UC400 takes 12-24V, and everything on the basic BOBs uses 12V (plus I think you need 5V via the USB for powering the step/dir outputs).