a lot of video synth stuff is analog.
If you look into stuff by LZX, they step into the digital realm as well.
There are some people out there in this FB group called Video Circuits who do some amazing things with vector scanning, illustrator, and various things like that.
I have seen some take to MAX MSP and pre render algorithms for both audio and visuals.
It all amazes me but some of it is way beyond over my head at this time haha.
So the idea behind the raspberry pi, is to create the a/v output, basically forcing the signal, and if you were to dirtily mix it, you could have an out of sync, attenuate-able visual signal 
So right now, I am using an NES to force an AV signal to a DVI/VGA Monitor as well as a powered converter. I run the NES into the dirty mixer and my casio SK-1 with a video out mod into the mixer as well lolol.
Its basic for now but fun.
I am totally going to build this dorkwave thing and add that into the mix 
As for newer tv’s. IDK. im poor. bahahaha.
Most visuals look better on CRT in my personal opinion. I wants to see them scanliiinnnneeess 