KLM Europe Select
Just flew them again, this time GVA/AMS/GVA with an F70 on the way there and a 737 on the way back. The service and food are indeed different between Select and Economy, though not much. You get food in a blue box that is quite pretty. I estimate that it costs almost as much as what is inside. Free papers. I could not say whether there is increased seat pitch towards the front, as you have on airlines with convertible seats.
The KLM description is here>
KLM Europe Select
Check in at our dedicated desks and head straight to the lounge – KLM Europe Select is our premium product for flights within Europe. You’ll enjoy fully flexible booking, advance seat reservation, extra baggage allowance, priority boarding and disembarking, and meal service on board. Plus, you’ll earn double Flying Blue Miles with every flight!