In the screenshot above I have a 3090 for rendering, and 3060 for OpenGL and display. In V-Ray device selection, make sure to uncheck your 1080ti when using RTX mode. And you will be able to dedicate your 3080ti to your GPU rendering, you will be able to access all available VRAM on your 3080ti here which is great! Locally-deformable PRT (Bat) 271 fps Avg. This is an excellent result which ranks the Nvidia RTX 3080 near the top of the comparison list. This way Maya, Max and all other applications will only use your 1080ti for viewport performance. The Nvidia RTX 3080 averaged 87.0 higher than the peak scores attained by the group leaders. In this case here you can use your 1080ti for Display/Viewport performance, to do that go to Nvidia Control panel, select Manage 3D settings, and look for 'OpenGL rendering GPUīy default this option is set to Auto-select, change it to your 1080ti

This way you will be able to have some spacing between the 2 GPUs, and they will run quieter and cooler, and they will boost frequencies higher

The 3080ti is much faster than your other 2 GPUs, I recommend to remove 1x 1080ti from this machine and keep 1x 1080ti + 1x 3080ti

It features 9,728 cores with base / boost clocks of 2.2 / 2. V-Ray 5 Benchmark 8x NVIDIA GeForce RTX 4090 24217MB 37 389 12x NVIDIA GeForce RTX 3090 24268MB 32 118 12x NVIDIA NVIDIA GeForce RTX 3090 24268MB 31 808 12x. In your case here it is best to stick to RTX mode, so V-Ray will be able to use dedicated ray-tracing hardware on your 3080ti to speed up your renderings The RTX 4080 is based on Nvidia’s Ada Lovelace architecture.

Rtx 3080 vray benchmark