I’m afraid neither of those things are supported out-of-the-box, and have no have user-visible settings or configurations.
If you’re willing to do some risky hacking some files on the device, they might be achievable.
For camera app from lock screen, the actions below will achieve that, HOWEVER launching a camera app this way will still require entering the lock code. Which means you get the same behaviour as with adding the Camera app to the “Lock Screen Shortcuts” in Settings.
So doing the latter is recommended as it doesn’t change system files.
To replace the app that is launched by swiping up on the lock screen, replace:
/usr/share/applications/jolla-camera-lockscreen.desktop
with the .desktop file for the app you want, and set the key NoDisplay=true in the .desktop file (this avoids having two icons in the Launcher).
Do keep a backup of any files you change, and revert if it does not work.