So this has been a question I've been dying to ask but I don't want to waste anyone's time on something I could solve myself.
I amended -gamescope to my /system.yaml file naturally give it a whirl & the following results return to me.
(I'll share the log file after posting, too long to copy/paste - so check comments bellow)
My natural assumption based on what I've read is that gamescope as a package is incompatible with the host system.
(I've tried many troubleshooting solutions specific to gamescope & system.yaml such as post_install:)
So naturally this seems like the perfect usecase for a container, without over bloating this thread with the same command on repeat.
The results were similar in my Arch/Fedora containers where I ensured Gamescope had neccesary packages needed to function properly.
So the Host & Container solution failed for the most part, I can share all of my troubleshooting steps but this is the conclusion I've come to I just more or less want know if I'm right or if something else could be amiss here.
Seems gamescope may want access to files its not privy to due to Read only file system.