1) Single HDMI cable from Oppo port 1 to AVR and then a single HDMI from AVR to TV
2) Single HDMI cable from Oppo port 1 to TV and a single HDMI cable from Oppo port 2 to AVR
In no case will you need to run two HDMI cables between the Oppo and the Denon. It's a matter of preference but personally I'd use choice 1 to let the AVR do all the switching so only one cable is connected to the TV. Ymmv.