I personally use Intel's QuickSync with OBS. I've tried all the encoding methods with OBS including NVENC, x264 CPU encoding, and an experimental AMD hardware accelerated encoder (which failed horribly). Out of all of these QuickSync gave the best performance and quality followed by NVENC and then x264.
If you have an Intel machine install their graphics driver and enable the iGPU from your BIOS/UEFI.
For recording I choose 30,000 to 35,000kbps (30mbps to 35mbps) since that's the limit of the write speed on the hard drive I save to. And to be honest at the resolution I record at, 30mbps is about the same as going with lossless encoding.