In Plasma5, one of the possible auto-hide options for the panesl was "Windows can cover", which means that the active window goes over the panel, while the inactive windows go below, but bringing the cursor to the edge of the screen would always bring the panel to the top.
This option is particularly useful, as it allows keeping the panel visible as long as possible, while also allowing maximized windows to take the entire screen.
In contrast, the "dodge windows" option dodges both active and inactive windows, which results in the panel being hidden most of the time, unless one is careful to avoid putting a window in the panel area.