I don't see anywhere in the config to disable snow accumulation. Is there a way to add specific blocks? Or to use a forge tag? Mostly I don't want snow accumulating on glass. Any way to do this?

There are two common config options for enabling snow accumulation: enableSnowAccumulationDuringWorldgen and enableSnowAccumulationDuringWeather, which are self explanatory. There is no way to add specific blocks. I suggest using a light source (see: vanilla)