This won’t matter as PyTorch ships with its own CUDA runtime dependencies and your locally installed CUDA toolkit will be used if you are building PyTorch from source or a custom CUDA extension.
I would recommend the latest CUDA toolkit (currently 12.1) as long as it’s compatible with your NVIDIA driver. Again, the locally CUDA toolkit doesn’t matter.
No, you need to install the NVIDIA driver yourself. The PyTorch binaries ship with CUDA runtime libraries, cuDNN, NCCL, etc.
No, you need to install an NVIDIA driver, but don’t need a CUDA toolkit.
Install an NVIDIA driver, then run pip install torch, which is enough to execute PyTorch workloads on your GPU.
I don’t respond to the other questions separately as they mainly target the locally installed CUDA toolkit which won’t be used if you install the binaries.