Another option - Take a Keikyu line train that connects to the Asakusa subway line and leave your bags in a locker at Asakusa, then spend your time exploring the Asakusa area. After exploring, take an airport keikyu train from Asakusa for a relatively slow connection to NRT or take a cab to Keisei Ueno station for the fast train to NRT.
When you consider using the Asakusa line, there are many possibilities like this.