The remote.conf files may be different, but the IR codes are likely all identical and already known.

I don't understand how your are going to learn these commands at all. Does each box come with an IR remote or the ability to output IR signals? Back when I used a Raspberry Pi running OpenELEC, I simply used an MCE IR dongle. The codes were known, so I didn't have to learn anything. But it's impossible to learn from an IR dongle anyway. I'm not familiar enough with these Android boxes to know their IR capabilities.

However, since remote.conf files are just LIRC, you don't need to learn anything at all. Just decode the files with IRScrutinizer and enter the data into RM.

If you can indeed send IR to a widget, then you could also send it to a C2 just as easily. The widget is nice to have, but the C2 can accomplish the same thing.

You are correct about the difference between the 15G and 18G. However, unlike the C2, the 15G is only 15 devices. You need 18, correct? You ordered a C2 and not a 15G?