Currently kscreenlocker doesn't hide the mouse cursor when locking. This is not optimal when using a bright cursor theme and a display vulnerable to burn-in (e.g. OLED). It would be best if it always hid the mouse cursor when entering locking, while mouse movement should make it temporarily return for a few seconds. Also, since the screensaver situation is dire on Linux, especially on Wayland, it would be nice if kscreenlocker could act as a screensaver without requiring password unlock after more than the current maximum of three minutes. In many home usage scenarios, users don't want to be required to unlock their own private system, e.g. when just leaving the room for a few minutes.
This bug report requests two changes; we need for each bug report to only be about one thing; see https://community.kde.org/Get_Involved/Issue_Reporting#One_issue_per_Bugzilla_ticket Let's use this to track the request to hide the cursor after a period of inactivity. That seems reasonable, especially for your use case of preventing OLED screen burn-in. As for the ability to have a passwordless lock screen, why not just set your own password to a blank string? If your security needs are so low (e.g. in a home setting, as you described) that you don't want to have to enter a password to unlock, maybe you don't even need a password at all? This is what I do for my shares family computer. No need for a password at all.
*** This bug has been marked as a duplicate of bug 432291 ***