Does nvlink help?

I have a machine 4x rtxes. Does install a nvlink benefit Pytorch?

nvlink is used for p2p communication between GPUs so in particular multi-GPU setups can be accelerated. The performance depends on your actual setup.

I have a setup with 4x 2080ti. My research mostly revolves around CV tasks using PyTorch’s DPP. Do you think it is a worthwhile investment?

I cannot give any recommendations to buy hardware and my best recommendation would be to check open and independent benchmarks for this or similar setups.