The foam certainly doesn't need sealed from moisture. It's completely inert when it comes to water.
As far as they plywood goes, you'll get both yes and no answers. Some people think you HAVE to seal the wood or you risk significant dimensional changes with humidity (playing hob with your trackwork!), while others think paint is not really necessary.
For myself, I don't paint the benchwork. I humidify my basement in winter and dehumidify it in summer. Most of the time my basement stays in the 40-60 per cent humidity range, which keeps the wood stable. Occasionally it swings beyond that (like when I forget to fill the humidifiers), but it takes some time for the wood to absorb or lose water, so a day or two of high or low humidity isn't a problem.