No preselection on KLM European flight in economy class, even for KLM elites. You can usually put in a request for an aisle or window, and elites do get to sit at the front of the cabin in general.
KLM pre-boarding seems to depend on the boarding area's layout: at gates where the boarding pass is scanned just before boarding, elites usually get a pre-boarding call. In AMS, boarding passes are scanned upon entering the waiting area at the gate, denying gate agents any means to screen passengers afterwards(they don't).