Is the Vulkan renderer stable for Yuzu
In order for us to provide better support, we need to see the log generated by Citra. This guide will walk you through how you can obtain the log file: How to Upload the Log File.
Is a Four core processor enough for Yuzu
If you have high CPU GHz it should work, for me with i7700k 4.20 GHz using 4 cores, I am happy how it works and if it needed I will go in hyper threading.