YOU NEED THE SCRIPT HOOK MOD TOO!!!!!!!!
With the Freecam mod you can fly all over RDR2's map, just not as a bird this time. You can move freely around the entire map—including parts you were never meant to see. Red Dead Redemption 2 does have a built in photo mode but the freecam gives you the ability to do a lot more. Andy Kelly got some great 4k screenshots like the above by using it to explore.