I purchased the Dell G7 15inch back in the summer and I have been trying to make it play nice with my 144hz screen for months.
The G7 laptop only has a HDMI and TB3 port to output video, while my monitor has HDMI, DP, and DVI. And the HDMI to HDMI is only giving me 60hz as an option.
I am using a TB3 to DP cable, and the computer in display settings is registering it CAN output 144hz. The UFO test likewise says I am outputting 144hz. But when compared to another computer of mine, truly outputting 144hz, it is night and day difference.
My Best Guess:
*I believe* that the TB3 port is attached to the intel GPU, and thus I am unable to use TB3 to properly use my 144hz monitor, I will post screenshots below. Likewise, When my computer is plugged in with TB3-DP, in Nvidia control panel, I lose all capabilities except 3D settings. While if I connect HDMI-HDMI I have all the settings in Nvidia control panel. Except then I no longer have the option in the settings to go to 144hz.
Please help, this has been taking way too much of my time.
The way that system is wired doesn't leave you any ideal option. As NVIDIA Control Panel is indicating, the HDMI output on that system is wired to the NVIDIA GPU, and the USB-C/TB3 output is wired to the Intel GPU. When your display is connected to the latter, the NVIDIA GPU can still be active through NVIDIA Optimus, which involves the NVIDIA GPU acting as a render-only device that sends completed video frames to the Intel GPU for passthrough to the display, but that passthrough design does introduce some limitations. However, it's not clear exactly what you're seeing in this "night and day difference" compared to systems that are "truly outputting 144 Hz". If Windows is saying that the Intel GPU is outputting 144 Hz, then it is; it's not just making that up. However, it's possible that NVIDIA Optimus itself is limited to 60 Hz, which might prevent 144 Hz from being used when the NVIDIA GPU is active. To be clear, I'm not sure that limitation actually exists; it's just a guess. I do however know that you can't use G-Sync through Optimus though, so if the other system you're testing has G-Sync enabled (and the display supports it), then that might account for the difference you're seeing.
As for HDMI, my guess as to why you're limited to 60 Hz there is either because the HDMI output doesn't support 144 Hz or the display's HDMI input won't accept 144 Hz. Some displays can only be driven at their maximum capabilities (resolution, refresh rate, G-Sync, etc.) via their DisplayPort inputs rather than HDMI.
If you're wondering why the USB-C/TB3 output is wired to the Intel GPU at all, it's mostly for battery life reasons. If it were wired to the NVIDIA GPU, then that GPU would need to be kept running whenever an external display was connected to that output, even if there was nothing graphics-intensive going on. Wiring the output to the Intel GPU allows the NVIDIA GPU to be completely disabled except when it's needed. On most laptops with dual GPUs, all outputs are wired to the Intel GPU for this reason. However, some gaming-oriented systems sometimes wire some or all external outputs directly to the discrete GPU in order to avoid the limitations I described earlier that get imposed when using Optimus passthrough. For example, running through an Intel GPU means you can't use VR, G-Sync, 5K resolution, or stereoscopic 3D, and possibly some other things. And then there are very high-end workstation models like the more recent Precision 7000 Series models that have a BIOS option allowing you to choose which outputs are wired to which GPU, but that's only available because those systems use a more complex and expensive motherboard design that involves the outputs being connected to multiplexers that are then wired back to both GPUs, so the user can choose which "path" should be used.