I use a couple of UC300s with UCCNC and I'm very happy with them.

I suggest that you avoid the 5LPT option. In fact, the CNCdrive site seems to show it as obsolete. I suspect that it was designed to replace controllers based on printer ports, and it uses 5V i/o signalling. The UCBB might be a better option with your ATC plans as it has plenty of i/o pins and can handle 24V signalling. This can be much more resistant to any interference, especially on a large machine with long cable runs.

You use idc connectors and ribbon cable between UC300 and UCBB. The UCBB has screw-down connectors for external wiring.