Consider using them for exclusive content or experiences.
Consider using them for exclusive content or experiences.
You've mixed things up. Typically, people pick two premium cards for SLI or Crossfire to achieve high resolutions like 1440p or 2160p, and/or fast framerates with a 120 or 144 Hz display. You should set a goal first to determine what you need. If you're playing at a standard 1080p at 60 FPS, the second GTX 970 is likely unnecessary—it won't make much difference beyond that. It might help with HairWorks in The Witcher 3, but that's the smallest improvement you'll probably see. In most titles, the two cards will struggle to reach 60 FPS and perform poorly.
I haven't seen many issues really, though I do run into them occasionally.