Please explain the difference you see between a chumra and a hiddur.
I don't know what he means, but it may be psychological.
A chumra restricts your behavior. either poor me, I'm deprived, or I'm so holy, look how much I give up for Hashem.
A hiddur enhances the way you do the mitzvah. You're doing more for your bond with Hashem, because it matters so much to you.