Yes, which is the default option on R4.2.4. So you’ve not overidden the R4.2.4 defaults to something else of your choosing yet 
Using qubes-prefs
(1), is one of the last steps you would take to enable a switch of the default_audiovm
(sys-audio) or default_guivm
(sys-gui) to a different qube(s). But first you have to build those qubes yourself, with the required and optional software, appropriate for your hardware platform.
I’ve found maybe 5 other repos from other authors too, which also deal with sys-audio and sys-gui in Salt scripts.
Couldn’t say I’m a Salt expert either - but I know enough to know to tell you - you probably don’t want to do that.
Salt scripts can call other Salt scripts within the repo’s structure. They’re often personalised to the author’s own system and/or own requirements. Here be dragons!
You might learn a couple things from reading through them though.
For sys-audio, the best source of information is still this Qubes OS Forum post: Audio qube
But it is a lot to read through, is not easy for a beginner who might be lacking foundational Qubes OS knowledge, and it (at time of writing this) has almost 350 comments on it - some of which are relavent to understanding the process.
It’s a great a resource. And at the same time, it can also be a chore if you’ve never successfully customized Qubes OS with a sys-audio.
For sys-gui, you’re on your own. 
Never done it before. There’s not a lot of people who have done it, and most who have are dev team or been on Qubes OS for a really long time.
It requires you to build a qube to support your own GPU card(s), and troubleshoot lots of low level hardware problems while almost certainly breaking graphics on your Qubes OS. Best of luck!