More clear documentation on how to change models

[Doranwen]

The documentation is sparse when it comes to how to change the model (say, the A1200 instead of the default A500 for an Amiga ROM) for the same core. It explains that it can be done either by the "Model" core option or by file path tags but neither method is fully explained. It also says:
You can pass .uae configuration files and they will be appended to the core option configuration.

I have scoured this a dozen times and searched the Internet ten ways from Sunday but have gotten no closer to understanding exactly how to implement one of these methods (or indeed, which one is best in this case). An example of this being done would help, especially since I'm also trying to figure out if this can be set using a Lutris installer. (This is such a specialized question that I'm not sure any of the Lutris folks know the answer - and I suspect that I need to understand how it normally works first before I can figure out if it can be done with Lutris.) If this is a really obvious thing and I'm just being really obtuse about it, I apologize - but I've been bashing my head against this for hours with no success.