LE 607 is an alternative to Mobil 1 and at the present time, there is no clear advantage of one over the other. The LE is extremely thick and requires warm up time. The Mobil 1 is more compliant with temperature extremes and has been used quite successfully for track duty. The choice is ultimately yours.
A good spark plug for an otherwise stock S2000 is the stock plug. Both NGK and Denso have supplied the platinum plugs that are OEM in this car. If you plugs have never been changed, it is time and there is a possibility that you do not have the updated plugs and the new recommended torque for them. Honda had a recall on the original plugs and when the replacements were designed, these incorporated a stainless steel crush ring and an increased torque of 18 lb/ft. You can't get the old plugs anymore, so no worries about that. Use anti-seize to install the plugs and gap them as per OEM spec.