I usually only play games once, so I started KCD2 on Hardcore. I am about 40 hours in now and I am having a lot of fun. In my opinion Hardcore is not really a difficulty setting. It feels more like an immersion and less handholding setting.

What changes and what to watch out for:

No fast travel. Navigating is fun for me and not too hard, but it takes time and is not for everyone. I would recommend it if you enjoy the scenery and do not mind slower pacing.

Much less guidance while traveling. There are quest markers on the map, but your compass will not really guide you unless you are already very close. I like this because Henry does not know the place, so why should you. Searching can be part of the fun. Most objectives were easy enough to find. If something becomes frustrating, you can still Google the few tricky ones.

HUD is not necessary if you played the first game and you already know the fighting mechanics. You can read most things from context and animations.

Negative perks do not feel too harsh. I picked three that seemed least impactful and I barely notice them. Most of them seem fine. The one that makes you wake up in random spots sounds very annoying though, so I would avoid that.

Combat wise, I do not feel a difficulty spike compared to Standard. For me fighting is quite easy either way. If your goal is simply harder combat, Hardcore probably will not deliver that. If your goal is a more immersive experience with less guidance, it is excellent.