The closest desktop GPU to the 870m is the 660Ti spec-wise, but about 10-20% slower at stock give or take the game.
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-870M.107792.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-660-Ti.110056.0.html
GPUz comparison: You see that you're in overclocking distance for the most part.
660Ti:
http://cdn.wccftech.com/wp-content/uploads/2012/08/MSI-GeForce-GTX-660-Ti-GPU-Z.jpg
870m:
http://www.bettasplendens.de/uploaded/P177SM/GPUZ.jpg
Your CPU is basically the same one I'm using. Being hyperthreaded, it is closer to the recommended CPU over all, but it is slower an the i7 4790 by 0.5GHz and so you. You can overclock the 4710MQ 200MHz. [https://www.youtube.com/watch?v=rwiiGGHsrxA] It doesn't sound like a lot, but it will [most importantly] help bump up your minimum FPS in CPU heavy situations. Of course, you have to be mindful of the temps. I don't know what model you have. Is it Dell, MSI GTx0, Asus, Gigabyte or Sager?
The "brute force" of the 870m's 1344 core count, 3GB of VRAM and the level of cooperation between Nvidia and Bethesda makes me think that you should hit mostly high settings on the big basic ones like texture, draw distance and some ambient occlusion, etc ...but go light on the MSAA and Nvidia's Gameworks features.