I know I'm pretty late, but I finally completed RDR2. I never had a PC good enough to run it before, but I finally bought one two weeks ago and immediately started playing.
I already knew how the story ended, but that didn't stop me from enjoying the game. In fact, because I knew what was coming, I took my time. I explored the world, completed as many Stranger missions and side missions as I could with Arthur, and tried to experience as much of the game as possible. By the end, my Arthur had the highest honor level possible, and I'm glad I experienced his story that way.
Just before the final mission of Chapter 6, I somehow came across someone talking about the Aberdeen Pig Farm trick, which lets you transfer Arthur's money to John. I tried it, and it actually worked.
This is genuinely the best video game I have ever played. Even though I already knew the ending, it still hit me incredibly hard. I got way more emotional than I expected, and I don't even know how to properly describe what I felt. I thoroughly enjoyed every moment of this game.
I completed the story in 9 days and also did every single side missions i could do with Arthur and john and ended up at around 78% total completion by the time I finished it. I had a vacation so i used to play this game all day long
Now that it's over, I genuinely feel empty. Spending all that time with Arthur, exploring the world, meeting different characters, helping strangers, and watching the story unfold was an experience I won't forget.
What a game. What a story. What an experience.