Ray -- I'm missing something in your response to Tom...? Doesn't a buck-boost system provide constant voltage (usually an adjustable set-point on the output voltage) - so it should provide constant light levels - or something close to it, should it not?? It won't if the track isn't powered, but I don't think that was what he was asking(?).
Tom - The boards I have seen on Amazon or eBay are typically DC in to DC out, so at least in your case, you won't need to use a bridge to convert AC to DC. A cap across the input would help with any flickering.