I don't really use KDE, and if I forgot some really crucial information thanks to correct me.
You can use the KDE spin version of Fedora with plasma 6, or if you love the rolling release of Arch you can try openSUSE Tumbleweed with KDE (you choose you desktop environment at installation).

And for what you going to loose if you go to GNOME :

• HDR (you can enable HDR experimental on mutter but not working for me).
• VRR (it's experimental on GNOME and work for me).
• You need extensions to customize your desktop, its not really a problem but some people don't want to many extensions (like me).
• Customization in KDE that you don't find in gnome, even in extensions.
• For Krunner you can use meta button to open gnome overview and start typing to find app.

And if you want to try GNOME try to stay the most "vanilla" possible. Some extensions I use :

• Blur my Shell
• Just Perfection
• Rounded Window Corners (need to do some search for each gnome release to find the new version)