I would def call old BoC and many other 80s and 90s oddball songs and releases "protovaporwave" (if it has the same sampling and retro emulation aspect) and/or unintentional vaporwave (if it's music that would make good fodder for vaporwave later on). There's also a lot of IDM peers of BoC that put out stuff similar to their music (Bola, Seefeel, Autechre, Dsjecta, etc).
I've heard dungeon synth, VGM, plenty of new age, jazz, world music, and soundtracks and a plethora of experimental and/or underground music from the 90s and early 00s that have vaporwave vibes. It's just scattered, random, and usually all unrelated to each other.
I should also add some of the best "vaporwave" I've heard has been released by people explicitly not part of the scene and/or self-described as such: 1991, Torn Hawk, Khotin, Sssaliva, even VHS Head at times.