Number of cores really helps, but your upload speed is the biggest factor.
You need to fine tune your bitrate with your framerate and resolution in OBS to get the maximum performance. NVENC encoding helps a bit too, but most work is still done on the CPU.
If you stream using Nvidia's overlay, you cannot fine tune your stream settings which means you will have a very inefficient stream. Even powerful setups struggle with Nvidia's software as it lacks a lot of features.
I would start by testing your upload speed, and convert that into kbps. Then you can assign a decent bitrate that is below that number. Depending on the bitrate, you can do 1280x720@30fps (2mbps minimum) and 1280x720@60 or 1920x1080@30 (5mbps minimum).
The more optimized your setup, the less CPU load you will have.