Can Smartthings work with devices already purchased from other systems such as one provided by a major home improvement chain?
Depends. Some of the Lowes Iris stuff works, depending upon if they’re items like the GE and Utilitech devices. The Iris motion, door/window contacts, and other items are not. Home Depot Wink stuff works, including the GE bulbs. I suggests doing a quick search on any device you may have questions about and I’m sure there’s already a discussion about it.