Really interesting topic; I studied Philosophy at Uni so this naturally tugged at my interests in morality and ethics..
I tended to play as honourably as i could, only killing when i had to, but sometimes while free roaming a little edge seeped in and i'd blow the head of a passer by just because i could. I think its human nature to experiment with morals in games. After all, if its available, isn't everyone going to experiment with what feels 'Right' to them.
I get more out of helping strangers than killing for no reason. I spend a lot of time trying to immerse myself in the atmosphere of the game so i'm naturally let by whats going on around me- for example in RDR any time spent in Thieves Landing i would generally wreak havoc because even if you're just minding your own business some good for nothing will pull their gun on you. So yeah, i think go with the flow and enjoy it- I aim to play as Arthur's personal morals lead me- if i see a change in his personality and lean to redemption, i will play as such.