Wi-Fi and zigbee interference has been discussed many times in this forum. See the FAQ (this is a clickable link)
Regarding Lutron, it’s a bridge, not a hub. And you have to have the Lutron SmartBridge ( or the smartbridge pro) in order to use the Lutron switches with smartthings, as the smartthings hub itself does not have a radio on the right frequency.
https://support.smartthings.com/hc/en-us/articles/115000864766-How-to-connect-Lutron-Caséta-devices
So any firmware updates are handled via the SmartBridge.