Jumping on the "luggage and other baggage strapped to first row seats" I can comment that the nice KLC purser just invited me to strap my backpack on the seat next to me (1C) since the overhead bins on the E-175 were already quite full. I wanted to propose that option just as she was telling me to do so. My backpack having a strap in the back on which you can place around a carry-on handle, I suppose that if you buckle it around that strap, it would be pretty safe in case of turbulence...