Maybe. Maybe.
One of the most important things to do BEFORE you start overclocking is to get baseline stability and temperature data via torture tests. So, at default everything, run something like furmark and looping unigine superposition, for 2 hours each. Record the max temps and look for artifacts. Once you have that info you'll need to do some research on safe temps for your RX 580.
Only then can you begin to determine the answers to your two questions.