High Honor has/had Arthur with High Honor, Low Honor has/had Arthur with Low Honor. Pretty self explanatory. Doesn't make much difference in the epilogue other than a couple lines of dialogue.

"Arthur" files are Arthur's last chance to freeroam right before "Our Best Selves" mission.

"Epilogue 1" is the Autosave immediately after the "Red Dead Redemption" mission, where you first take control of John.

"Epilogue 2" Is right after the "Motherhood" mission when John is first able to fully freeroam.

Aberdeen Pig Farm has $6339.35. Visit the map marker to collect this cash. (only available with Epilogue 1 and 2 save files; you can still do it yourself though with the Arthur file, just go to Aberdeen pig farm, have them steal all of Arthur's money by accepting their drinks/food, and then come back to the house as Marston to collect Arthur's cash).