DDMF's VirtualAudioStream does that. It allows you to create virtual audio devices with chains of arbitrary VST plugins. As for the VST plugins, there are thousands of free and paid plugins for everything. I'm using VirtualAudio stream to put a Wave's noise cancelling and a good compressor between my mic and Zoom. It increases latency, of course.
I think so. TBH I'm quite new to the world of DSPs so I don't know the right terminology. The purpose of the DSP (which I should've mentioned in my original post now that I think of it) is to tweak the speakers on my laptop - there are for example ways to "fake" bass (through missing harmonics), or have dynamically changing bass. I'll have a look at VirtualAudioStream, thanks for the recommendation.
Text based: SuperCollider, Csound, Chuck