A lot of data center GPUs don't have display outputs or cooling. So you would need to figure out how to cool them.

A cursory search says somewhere between a 3060 and 4060, which seems about right. Games that parallelize well across the GPU cores will benefit, though that benefit will be niche if it exists at all. HBM2 memory is weird for gaming.

You'd see some benefit for sure, but this really is better suited to parallel computing, given the emphasis on CUDA core counts and memory bandwidth. You may also find you run into some latency, since it requires selecting the V100 as your primary GPU but a secondary card as the video output. Integrated GPUs work well for this, since your motherboard may already have this ability. Otherwise, you could use it in tandem with a 1030 or similar to get display out.