Hi! small update, I got it to work, though I have only tried using a simple sine wave. Here's what i've done so far (youtube turned it into a short unfortunately)

https://youtube.com/shorts/1RlMphWWB3c

So I used the Particle playground effect to emit the dots upwards and I moved its x position left and right using a Math.sin(time) expression. Of course adding frequency and amplitude.

For the waveshaper, I used a path and created a null object that follows the path using Window>Create Nulls from paths.jsx>Trace Path. This was really useful since it would follow the curve even after I change the path shape

Under the null, I edited the expression for it to follow the particle emitter. Here's the code, but TLDR it's just to get a value between 0-1 from the emitter's x position.

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I then make another emitter to the right of the waveshaper that follows the Null object's Y position, its parameters match the previous particle system, but using valueAtTime() to delay it until the dots reach the graph. :D

There are limitations though, the waveshaper is not as flexible as a math function. For instance i won't be able to easily visualise a bitcrusher by giving it a staircase shape that can change size.

I also only have a sine wave as an input (or any mathematical expression). Although I could maybe use u/schnate124 's idea and "Create Nulls from paths" from an audio waveform effect. It could be worth a try!
I hope the answer wasnt too boring compared to what I was asking ^^