At this time, multi-GPU support for Twinmotion is limited and not officially supported.
Our 2023.1 Preview 2 update will add multi-GPU support for use only with Path Tracer, where multiple GPUs can be utilized to increase Path Tracer rendering speeds. Multi-GPU use will not increase available VRAM capacity and usage for Twinmotion, which will be limited to one GPU. Only Path Tracer render times will be improved by this. Multi-GPU will require two identical graphics cards that are connected using NVLink. Compatibility and support for AMD multi-GPU is being investigated.
In your case, I do not believe the RTX 3060 supports NVLink (I believe only the 3090 from that GPU generation supports NVLink), so your computer won't be able to benefit from multi-GPU support. The best option to improve standard, rasterized rendering times would be to upgrade to a single more powerful GPU.