I’ve recently made two posts about the keyboards and for the encryption there’s a bug report about unl0kr in Bazzite where I added a comment. Unfortunately I don’t have the energy for a more detailed writeup, but it should be enough to get you started.
The controller works out of the box as a mouse. You just need to have an on screen keyboard installed (or a real one attached via USB) to handle everything else. If you like Gnome that should actually work better out of the box than KDE.