I don’t like the 72D harness. You don’t NEED an overcheck, so that is extra to pay for which you probably won’t use. Snaps on the breastcollar are easy breaking point, lazy way to take off. Horse should be able to put his own head thru straps to put breastcollar off and on.
A stiff back on the harness saddle, even fuzzy padded, won’t keep weight off the horse spine with a 2-wheel vehicle. Weight will make him sore backed, inhibit his action, be tiring on long drives or with heavy loads. Buggy harness is for horse with 4-wheels, no shaft weight. Saddle with no tree, is cost cutter difference between a Cart harness with the tree (2-wheel) always having shaft weight of vehicle and passengers on horse back. Buggy harness (4-wheel) only having to carry shafts with no weight so they often get away with no saddle tree or ignore the results in horse movement.
Fuzzy pads can be colorful, easy to wash for keeping harness clean. However they compress under shaft weight of 2-wheelers, so not really that good of padding. Often sponge inside. They don’t protect the spine, beyond maybe letting the harness saddle rub a hole in horse with 2-wheeler shaft weight.
Strapping width on breastcollar “looks” narrow, as does the saddle. You said 4", but doesn’t look that wide to me. Narrow widths cut into horse more.
I really don’t care for the little buckles on the bridle. Ones I have seen have little wire tongues, not up to much strain so buckles will fail you when strength is needed. Other buckles on harness appear to be Conway buckles, which can be hard to use, adjust easily. Looks like you get a bonus of hip rings for the reins. They can work well on long relaxing drives, but will dull the horse rein signals a bit. Not a show accessory.
For me, the $600+ price tag is too high for what you get. I would not be shopping there.