Any two, meaning pick two per time a player pays 100xp or you can pick two and then the option is no longer there and that cost 100xp per selection? Its displayed differently than sound constitution in the Core book, but it is a different book so, worth the question I think.

The way my Blood Raven has been buying them is 2 per 100 exp. Good luck, the character sheet does not provide THAT much room for lore