Unreal engine is pretty bad for open maps. It generates a lot of cpu usage when changing zones. And heavy textures and other heavy elements don’t enhance the experience.

The vram, I’m not sure what your questions is about.

The vram is special ram (much higher bandwidth, but slightly higher latency than cpu ram, also supports special extra things) included on the board of the graphics card.

It is necessary because it stores textures and others game elements the graphics card needs to operate the game (shadow info,…). The elements are loaded into vram, from the very slow (in comparison) drive (even nvme 5.0 ssds are extra slow compared to vram or ram) to allow the gpu to process whatever it has to do. Background tasks, windows, the desktop… Also use vram to be able to have the app windows and desktop displayed, so the total available for the game can vary.

If there isn’t enough vram, there can be multiple things happening (I’m talking about textures but vram includes others things too) :

• Resizable bar ( or SAM on amd) is not enabled : the gpu will not be able to load all the textures, so it would either have missing textures, or lag a lot due to texture swapping. The textures can also take a lot of time to load instead of completely missing depending on the game optimisation, due to swapping with previous textures. The game can even crash.

• Resizable bar is enabled : it is possible with this pci-e configuration for the gpu to access system memory. So in some cases, textures may spill into system memory (cpu ram), which isn’t great either, because system memory has a way higher latency to the gpu (it has to go through the cpu, pci-e slot…), and way lower bandwidth. And so generates lots of lag.

If a game is well optimized, the lower the settings are the lower vram usage there is. Some games however did not have such great optimisation. Vram usage mostly depends on the texture quality and resolution. (increasing the texture quality will use a very few/negligible amount of extra gpu power, but increase the vram usage).

There is also a baseline the devs may put for optimisation. The less vram there is, the less the textures can have data available to use. So the more compromises have to be done, with less and less quality. So fixing a baseline quality depending on the current most used vram capacity is not that bad. Tho it does have issues for people having less available.