Ctrl-Virtual Keyboard is pretty vague:
Is this a pop up telling you that you can press Ctrl (and something else) to get a virtual keyboard,
Or is it a virtual keyboard popping up
Or is it a KDE Plasmoid on your desktop?
Maybe post a screenshot?
Use pamac (or what ever you prefer) to see if the package named qt5-virtualkeyboard is installed and maybe uninstall it.
I've no idea why that would have been installed, it is not on any of mine. Maybe there was an issue with your keyboard at install/update time and it decided it had to add it as a fail safe.
Programs started at login in KDE:
These can come from two different sources
1) the start up Programs list that you mention
2) The desktop session settings (also accessed from kde system settings (startup and Shutdown menu). If the On-Login section is set to "restore previous session" it will do just that, and restore what ever was running at last logoff. Try setting that to Empty Session, then logout and log back in. No reboot necessary.