I think you see the problem now. I'm playing in 4k on max graphics settings.
EDIT: Also, only the caged cockpit from AirplanesPlus seems to be affected by the white texture thing, other parts work fine.
I'm using the version of Procedural Parts that's on CKAN.
EDIT2: Checked out the files. Yep, the textures do come in that resolution, it's not the game's issue. Maybe the archive (or GitHub) compresses them?
EDIT3: Procedural Parts seem to work. I'm an idiot. I thought procedural wings were part of that mod, they aren't, they're from B9.
EDIT4: Apparently I had v0.4.0.0 installed, even though I downloaded it yesterday... strange. Trying out the new version... nope, same issues. It really has the low res textures in the pack by default, 256x256 compared to vanilla's 1024x1024.
EDIT5: It also overrides Procedural Parts textures when you launch the aircraft, even though the editor shows the texture selected last, and even if you select a stock texture... *sigh*