We need to know what the UI will be. Will we just have a minimal install? Will be do a minimal desktop like XFCE?

For starters, I will probrubly just do a minimal install, to make sure the kiwi configurations are working correctly.

Ideally there would be images corresponding to what is available on Fedora:
https://alt.fedoraproject.org/alt/
But a minimal image isn't a bad place to start.

Fedora KDE officially supports AArch64 as a SIG now, so I would probably just start with Minimal and KDE.

Another thing to consider is installing by default the fedora flavored kernels from the Kmods SIG so that a wider range of SBCs can be supported by CentOS Stream

That will require more setup, as we need build tags to consume their kernels. Please make a separate issue for that.

You may want to look at the Fedora-ELN configuration work done by @sgallagh. That's in the fedora-kiwi-descriptions repo but uses configurations that work with stock CentOS/RHEL.

Thank you, I will.
I'm putting the links to them here, so I, and others, won't loose them.

https://pagure.io/fedora-kiwi-descriptions/blob/rawhide/f/components/boot-eln.xml
https://pagure.io/fedora-kiwi-descriptions/blob/rawhide/f/Fedora-ELN.kiwi