That game is early access, so no one can guarantee framerate. These are budget CPUs so you probably want the faster one if they both cost you the same. I don't think the 860k is so much faster that I'd pay extra for it. Finally, the RX 460 is meant for 60fps at 1080p in esports games. Battlegrounds is not in that category, so to get smooth fps in that game with a 460 you'll probably need to play at 720p, and even then you'll only get framerate as high as the CPU allows.