I would decide on either the SHC300 or FG400. If you feel you don't get the cut you wants with the GG mf finishing pad you are useing if it's that in the picture you have. Some paint don't like finishing with mf polishing pad. I would recommend if you like GG polishing pads to look at the BOSS pads. There are a simple line of pads and would suit your GG 6" polisher great with a 5" backing plate on it. The pads are 5.5" to that backing plate and is thinner than the regualar line of pads.
Griots Garage 5.5 inch BOSS Foam and Microfiber Pads
It looks like you got great results. But 2 steps polishing would cut down the time. Then again test spot and inspect with a good lighting and a panel wipe product or ipa wipe down. Will tell what you get from the polishing. It's hard to see from pictures if those is not taken with a lighting source or in the sun. A camera with the flash on you can also get some inspection pictures with.
The wipe off of the polish can be hard if you overworked it. Or use alot of polish or to little of it. The environment you polish in plays a part to. And the best way is to use a quality mf towel for polish removal. I link to some good ones. And I have the Sonax towels myself and they are good and 2 sides with different nap. To use the side that works best. Often both sides works good. Wash the mf towels even when they are new. And use a microfiber detergent like 3d Towel Kleen to have clean and great performance from them.
Sky Blue Edgeless Polishing Cloth
SONAX Ultrafine Microfiber Cloths
How many passes per sections do you do when polishing?
And how many pads do you use with each polish?