Oo thanks for sharing the cool music.
For the strxwberrymilk example, it sounds like just a chopped and screwed dialogue. What I would do to imitate it is chop up a sample of dialogue and import each slice into a sampler on different pads/keys, that way I can "play" the part in that I like. (Alternatively, you can arrange it on the grid too, dragging and dropping slices.) I might follow that with a formant shifter for that kinda chipmunk sound.
Similar thing for the BoC reference: but it sounds like some of the slices are very short and loop, creating that stuttering, robotic sound, almost oscillating in the audible range. It also sounds like the part is also being panned around the stereo field. I might add flanger to capture the psychedelic feel too.
Love the stuff by ChowDSP.
AudioThing and TAL have some handy freebies.
There's a whole treasure trove in Airwindows' stuff.
I get a lot of use from Reaper's stock plugins, particularly the EQ, compressor, and limiter.
Reaper users can also help themselves to community-made JSFX.
Vital is my go-to synth.
Cardinal synth is super powerful and a fun can of worms.