My Profile's Shipping Address card always updates your account address instantly, and if you have an active subscription it asks whether to push that same update onto the subscription too — choose Just profile to leave the subscription alone, or Yes both to update both at once. The separate address form on My Subscription behaves differently depending on the business's own setting: by default it only sends staff a request to review before anything changes on the subscription; but if the business has turned on self-service subscription address changes, that form instead updates the subscription's address immediately as well, with no review step. So the real difference isn't "instant vs. request" — it's the profile page's optional cascade to your subscription versus the subscription form's own request-or-self-service setting.