XPS 15 9560 144 hz monitor

All of the display outputs on that system are wired to the Intel GPU (the NVIDIA GPU operates through Optimus), and unfortunately I don’t know if it has limitations around max refresh rate. However, in terms of PORT capabilities, specifically available bandwidth, the HDMI output is 1.4 and the USB-C/TB3 port carries DisplayPort 1.2. The latter allows more bandwidth when used with a USB-C to DisplayPort cable directly attached to the port, so it would typically be a better choice, and if your display supports 120 or 144 Hz and has a DisplayPort input, the overwhelming likelihood is that it will work at that refresh rate if connected using the type of cable I just described. Technically there are also DisplayPort 1.3 and 1.4 standards that support higher bandwidth, but I haven’t seen those used for high refresh rate displays yet, so DP 1.3 or 1.4 shouldn’t be required to use the advertised capabilities of the display. Even the 4K high refresh displays at the moment work on DisplayPort 1.2 by doing things like chroma subsampling at the higher refresh rates.

Note however that even if the Intel GPU supports high refresh rates, it will NOT allow you to use G-Sync, because either the Intel GPU doesn’t support passing it through and/or it only works when the NVIDIA GPU has direct control of the display output, which isn’t the case in an Optimus setup. Adaptive V-Sync also doesn’t work for the same reason. As a result, running high refresh rates can become a bit of an issue, because your only options are V-Sync On or V-Sync Off. The former is difficult if you’re running a high refresh rate unless you want to reduce detail settings to make sure the GPU can always sustain a frame rate that matches the display's refresh rate (otherwise you see judder) and the latter is difficult because it allows frame tearing. This is the exact dilemma that G-Sync is meant to solve by allowing the best of both worlds where you have no tearing AND no judder because the display’s refresh rate will adjust based on what the GPU can deliver at any given moment, but that’s not possible with this system.