I think a protectant is likely more than is needed, but up to you. As long as they are clean and stored properly the winter rubber should be well. You might check with a tire store on proper inflation while stored.
I dress them before storage because when I put them on it's snowing, cold and late and the last thing I would do is dress them.
Not that it make a difference durning a snow storm............
Need to get some of that Tire Bling the Spanish guys like