You use the simplest, but not always correct solution.
x264 is a software encoder that uses CPU resources. The processor has to constantly reallocate resources between the system, game and coding. This is not justified in terms of performance. If you have a slow CPU, it will only get worse!
NVENC works very differently. This is a separate component in the video card, which is specifically designed for video encoding and takes all the load on itself.
Most likely, you have old video cards and after the OBS update, settings are enabled that are simply not supported, which is why you get an error. To see this, need a log file.