There are several types of fidelity, Temporal, Spatial and graphical.
Temporal covers the fps and the tearing/stuttering free experience, this is important, and it affects the ability to enjoy the game, you get this by having the latest Adaptive Sync displays, with the highest refresh rates. eg: 166HZ GSync monitor.
Graphical covers how each pixel is lit/shadowed or receive detail such as textures and polygons, this is important as it affects immersion in the game, you want to create the best possible virtual world, by maxing each graphics settings available. You obtain this through better processing. eg: 5 GHz 8 core CPU and a 1080Ti.
Spatial covers the resolution of the game, and also the Anti-Aliasing portion, the higher the resolution the sharper the image, less aliasing and the more details you can see at large monitor sizes. HDR is a property of the monitor as well, and is made through spatial technologies in the monitor itself (dimming, brightness). This affects the ability to see the game without distraction, You get this fidelity by buying a bigger HDR screen and more processing. eg: 40 inch 4K HDR enabled screen.
Every fidelity type is important, you get all of them by having the best screen possible with the best hardware. The screen portion is mostly passive, it won't cost you processing power, HDR, G.Sync, 166Hz. However the hardware side is costly, you want the best GPUs for native resolution and max graphics.
The best fidelity is obtainable like this:
1- 34 inch 4K 120Hz+ screen, (screen size to resolution ratio is high here to maximize sharpness and reduce aliasing)
2- TitanXp or 1080Ti, sadly this is your only choice, as this is the most powerful single solution
3- The screen should be HDR enabled (1000 nits) with G.Sync (your only choice after 1080Ti)
You can of course compromise by choosing a smaller screen:
1- 27 inch 1440p 120Hz+ screen, HDR enabled
2- Vega 64 or GTX 1080/ Vega 56 or GTX 1070Ti
3- The Screen should be FreeSync or G.Sync depending on your choice of GPU