Using hardened Kernel on Kinoite or in general?

There is a pretty updated COPR including hardened_malloc and kernel-hardened.

These should be included in Fedora by default, but I am wondering if I can just install the packages, what would happen?

On Kinoite I enabled the repo (by manually writing the .repo file, as I dont know a version-agnostic command) and installed hardened_malloc.

It is low layered, will it work, or do I have to uninstall the regular malloc first?

Can I just layer the hardened kernel, or will it be too recent and break things?

I tried this:

sudo rpm-ostree override remove kernel kernel-core kernel-modules kernel-modules-extra --install kernel-hardened

All dependencies are fulfilled, but I still get this error:
error: Multiple kernels (vmlinuz) found in: usr/lib/modules: 6.1.8-hardened1-1-hardened 6.1.7-200.fc37.x86_64+debug