I haven't used Pop!_OS much lately, but from what I remember at the time I received the system with Pop!_OS preinstalled there were options in the main menu (alongside shut down / reboot) to switch between integrated and discrete graphics. The change involved a system reboot, and there wasn't any support for hybrid graphics.
This is new to me! I'll try it out one of these days. Last time I dealt with this stuff bumblebee was still in use. There was also a hack to spawn a second hardware-accelerated X server.
The primus-vk-nvidia stack still uses Bumblebee. It replaces the original PRIMUS component with a version that shares the image data through the Vulkan APIs, which seems to have fewer issues with incompatible OpenGL versions (even when both the app and the compositor are using OpenGL and not Vulkan). Perhaps something about Vulkan being designed from the start to support multiple vendor backends in the same process, vs. OpenGL where you generally have to load a single vendor's implementation?
They have dedicated nvidia GPUs. Due to the poor state of proprietary nvidia drivers, there's no hybrid graphics support. The kernel can't turn the dedicated GPU off and switch to integrated graphics. So it just stays on at all times and those things consume a lot of power. I actually measure the power draw constantly using the nvidia management library and it's very interesting to see all kinds of random software suddenly trigger massive power usage spikes. The hardware-accelerated kitty terminal is a major offender. Turning off the GPU in the firmware settings extended battery life to about 6-7 hours.
Maybe system76 worked some kind of miracle here and got hybrid graphics working? That would be amazing.