I tried running Doom on my office machine in 4K. It ran smoothly in 60 FPS and looks amazing.
I tried playing this through GeForce NOW with a virtual on-screen controller on my Android phone. It works, it's not too laggy, but a physical controller seems necessary.
Another attempt at GeForce NOW, I tried connecting a PS4 controller to my Samsung S7 using BlueTooth. I learned that non-first generation PS4 controllers connects to Android phones without any issue (using the Share+Playstation button trick), but this doesn't work with early controllers. However, after connecting the controller, I was disappointed with a ridiculous amount of controller lag (around 1s). I verified the problem by 1) trying the on-screen controller, which was relatively lag-free, and 2) disconnecting my BlueTooth headphones and playing something on RetroArch, same lag. Unplayable.
I played through the first mission in 4K >60FPS on my awesome work computer.