Heat set inserts are an interesting topic. You don’t need them if the screw is only installed once. Sure enough you can drive a metric screw into a 3D-prind and form/cut the threads but better are self tapping plastic screws. For nut vs. insert: It depends. if you can get away with a square nut (e.g. DIN 557 | don’t use hex nuts like DIN934) they are quicker to install. Make the cutout slightly undersized so the nut is fixed/wont move when the screw is installed.

If you use inserts consider the flange type to get a very nice aesthetic: e.g. de.aliexpress.com/item/1005006135129074.html

Removable plastic rivts are also a great fastening option. Push pins with integrated spring are equally briliant. Parts with snap fits are awsome but very diffuclt to design as the tab needs to flexible to be pushed in place but still strong enough to not break (layer adhesion).

Warping is indeed a big selling point for these materials. Major selling point/driving force I belive is still the esthetics of them as they provide a surface finish which can be sold (without post processing) without looking like a FDM 3D-print. Less warping, improved properties is more of a nice to have for most applications.

don’t seem to be, at least at the hobbyist level

This can be sad about a dozens of constructions. ISO1234 /DIN91/GB91-2000 splints are everywhere in the industry but nobody in the hobby space knows about them.

It’s pretty common to see cheap bearings in 3d printed parts, actually mildly interesting to me that bushings don’t seem to be

For bushing vs. bearing: It always depends on the application and industry.

. Do wonder though about the wear of 3d printed bushings, surfaces won’t be smooth,

Talked a while ago to somebody that run studies on FDM printed bushings. The verdict was that print orientation/layer adhesion was a limiting factor with their setup.