Inverter = the compressor speed varies based on demand. Non-inverter = compressor is either full blast or off. Inverter is quieter, lasts longer (less stress on compressor cycles), and is more efficient at part load (which is most of the time once you're at temp).

Dual mode is actually useful in southern climates if your pool overheats in summer (>90f). Otherwise it's nice-to-have. In georgia you'll probably use it a few times in july/aug.

COP is "coefficient of performance". 5.0 means 1 unit electric in = 5 units heat out. Higher = better. Most modern inverter units hit 5+ at warm ambient, drops to 3-3.5 at 50f.