I am quite disappointed with the performance of this exact combination.
Yes, the results from the optical magnification of the 1.4X III converter are better than interpolating the image to larger resolution. However, it noticeably diminishes image quality and contrast. Perhaps resolution might be fairly high, but the punch just isn't there for me. For an equivalent, I would say that the 7D with the 70-200 mm II is just as good as the 5D3 with the 70-200mm II + 1.4X. That's not supposed to be a positive comparison. I used both combinations for thousands of photos just a few days ago.
It's better if possible to just get closer with the 200mm lens and forgo the 1.4X converter. The 1.4X III converter does amazing things with a lens that is far sharper to start with like the $5,000+ exotic lenses. But the 70-200 II lens with its huge number of elements doesn't exceed the camera's resolution by a sufficient margin to maintain its quality when combined with a teleconverter. Only the lenses like the 300mm f/2.8, etc., can do that.
5DIII, 5DII, 7D x5, 6D, T2i, T3, 1D X, 10-22mm, 16-35mm II, 18-55mm II, 18-135mm IS x2, 70-200mm f/2.8L II, 24mm f/1.4L II, 50mm f/1.4, 50mm 1/1.8 II x2, 85mm f/1.8 x2, 100mm f/2 x2, 135mm f/2L x2, 200mm f/2.8L II x2, 1.4X III, 2.0X II, 60mm f/2.8 Macro, etc. only had room to list a few Canon items