You should always use the MAC address reported on the LCD display of OpenSprinkler. The WiFi adapter (assume you’ve set it in client mode) is a simply pass-through, so don’t use the WiFi adapter’s MAC.
For additional details, we have a tutorial video on how to set up fixed IP, and port forwarding:
https://opensprinkler.freshdesk.com/solution/categories/5000022938/folders/5000099521/articles/5000569763-video-how-to-set-up-port-forwarding-for-remote-access