JACK should cover all your needs. I’ve never needed a SAR or voicemeeter equivalent on Linux. The default bridge setup is a stereo mixdown from pulseaudio into the JACK ecosystem. You would need to mess around with multiple sinks as part of the pulseaudio jack bridge if you wanted to manipulate or record each application to a separate track: https://askubuntu.com/questions/680817/jack-and-pulseaudio-multiple-sinks
On Windows, it seems that SAR or Voicemeeter are kinda the equivalents of the Linux pulseaudio bridge. I should also point out that if you want to stick to a stereo mixdown approach, you can always use the pulseaudio mixer as a way to balance your various applications before they reach JACK.
That sounds about right other than, as I mentioned, you can leave out the multiple sinks if you use the pulseaudio mixer to balance everything to your satisfaction. I guess it depends on whether you need to do adjustments to each individual application’s audio after the fact.
I will have too look more into that when I do the linux version first I am setting up windows cause I already have all the application and stuff on here and most setup except ardour.
When I get a working product I might record a video showing the entire process of it being done on my second machine on clean windows install and then doing it on linux and posting about it on my website.
If I do do that I will provide a link. If anyone would want it.
I checked out ardour I already got it too work and it is actually much better then I was expecting cause it automatically labels the inputs and outputs. I actually found out on windows I dont even need jack anymore I only need asio4all cause I dont have a asio card unless I missed it will check later on that and ardour and SAR.
Edit: I was gonna respond ealier but apparently there is a daily limit for new users so I could not.