RE: Controlling DP and HDMI port settings on Precision 7720?
I'm not sure this still exists for the 7720, but the 7710 (and 7510) had an optional "Graphics special mode" in the BIOS that forced the discrete GPU to control of all external display outputs. By default, the integrated GPU is used for those outputs (except the underside dock connector) and the discrete GPU is only enabled when Windows/drivers detect that its additional horsepower is required -- but even then, operates as a render-only device that passes completed frames to the integrated GPU for output rather than controlling the outputs directly.
Typically the only time you would need the discrete GPU controlling outputs directly would be if you're trying to use a display setup that isn't supported by the integrated GPU, such as a 5K display that doesn't support DisplayPort 1.4 and therefore requires TWO DisplayPort connections. To use such a display with your system, you would either connect a DisplayPort MST hub to your single DP output and then two of the outputs to the same 5K display, or use a TB16 dock. Either way, the Intel GPU would not support this configuration, but the discrete GPU drivers would, which is why Graphics you'd have to enable "Graphics special mode". Another case would be if you needed to use something like G-Sync.
But unless you plan to do something like that, even if you find that setting on your 7720, I would start by keeping it disabled. Running your discrete GPU that often will probably reduce your battery life significantly, and even if you find that the discrete GPU isn't running when you feel it should be (the difference will be obvious), you can usually tweak the drivers to make sure that the discrete GPU runs whenever a particular application is running. Start with the default settings and tweak as needed. 🙂