Splais,

Maybe I can add a little to what you found on the sites.

The pattern rc planes are not scale models. They are designed to be rc planes. Small pattern planes are around, but most of the current designs are fairly large. They have a size and weight limit.
They are limited to 2 meters in wingspan, 2 meters length, with about an 11 pound max weight. They are not designed for 3-d type stuff, but rather smooth and accurate control.

IMAC planes are scale models of full size planes, 1/4 scale or larger, athough in the beginning level of competition the plane can be smaller.

Both categories fly a lot of the same maneuvers as diagrammed in the Aresti system, although pattern and IMAC have different sequences for competition.

I hope this helps.

Larry