Yes, you may leave Amsterdam airport. There you will erase the Schengen immigration controls, through which your passport will be sealed. After that, there will be nothing preventing you from leaving the airport. Be sure to leave enough time to return to the airport, go through the airport security and find your boarding gate. There will be no immigration controls for your flight from Amsterdam to Luxembourg, although you must show your passport as identification to prove that you are the passenger on the boarding pass.
Normally, you will claim your luggage at your final destination. However, there may be exceptions due to unusual circumstances, so be sure to pay attention to what the airline agent tells you when you register your luggage.