RTX could be helpful, but I never have seen a big speed improvement, maybe 0%…10% most.
CPU+Cuda can be helpful, but some times not. In my case the CPU is needed to feed all GPU. If the CPU is used for rendering too, than the GPU get less data and the rendering is slower. CPU Cuda is only emulated GPU rendering. But in your case it could help. I would look at the V-Ray benchmark results and look for CPU and GPU results.
GPU 6GB is quite limited, I hope you use a second GPU for display use.