For the purpose of configuring for non dedicated STBs (like the MAGs or AVoVs), the MAC is entirely arbitrary. You can set it up to whatever you want, as long as it starts with 00:1A:78, and no one else is using it. You shouldn't have to change the MAC if you to a different box or client, but if you want it to avoid an IPTV Reset, you have to make sure the device info is the same (Serial Number, Device ID, Device ID2, and Signature, but only the first two are required).
As far as your box, you get what you pay for, but I run Kodi on some very generic devices with no issues. I don't know about the build that you have, but they screw up personalized settings. As far as what you see as a MAC in the Kodi system info, it's whatever it is connecting to the outside internet, so if its going through ethernet, its using the ethernet network adapter's MAC or if its going through the wireless, then its using that network adapter MAC. It has nothing to do with the IPTV Stalker addon MAC, which I said was 'arbitrary'.