Goodman is owned by Daikin
And to the best of my knowledge, they are manufactured in house using their own designs.
Carrier owns ICP who markets arcoaire, Tempstar, Comfortmaker, Heil, Day & Night, and Heil.
Rheemn/Ruud one of the same.
Lennox makes Lennox and a subsidiary called Allied Air markets Air Ease, Concord Ducane, and Armstrong Air.
Nordyne (cursed microchannel crap) makes Intertherm for mobile homes, slaps a Maytag and Frigidaire name on their stuff.
Coleman is a subsidairy of York which in turn is owned by Johnson Controls.
Trane is trane I believe
Bottom line, beyond the actual heat exchanger design and construction and the outer cabinet, everything else is off the shelf parts. Inducer motors, HSI devices, blower motor, gas valves, etc. For the most part, you pay for large marketing programs and dealer markup. And the name of course. Ask Trane how well it works. People will pay top dollar for a Trane that beyond the aforementioned stuff, is pretty much the same box as everyone else.