In KDE4 times when I use a folder view applet in the panel, it behaves like a popup menu: clicking the folder view icon pops up the list of files in the defined folder, doing a SINGLE click on one of the files opens the application for it (Important: I have definded to use DOUBLE-CLICK to open files from konqueror etc. in kcm-mouse) That was very conveniant and a quick way to open my files. In plasma5, this does no longer work that way. I need to DOUBLE-CLICK the item in the popup to open the application. I checked and it follows the global mouse-click selection. More convenient would be to act as it was in KDE4 times Reproducible: Always
This is intentional, it's a file manager view. The setting in System Settings also refers to "opening files and folders", so not following it would be really weird.
weird are the continuous changes in behavior between KDE4 and 5 and no way to configure the old one.