Glad to see another (semi BPRC anyway, if you take the BP off) convert!!!
I have 2 RailKing 2-8-0s using BPRC and they are indeed some smooth running engines.
For your headlight issue, you either have the 2 wires crossed or a setting in the Bluerail app that needs to be changed.
Bob Walker has helped me in the past so give him a shout if needed.
I haven't bought the newest BlueRail board yet,have nothing to put it in at the moment.