I have an RX 580 and yes without setting the Power Limit at +50 and using custom fan and temp settings it throttles making it slow and destabilizing the system.
Here are my RX 580 settings that are 100% Rock Solid for me:
Then I do the following in Windows to make it even better:
1. Disable Fast Startup / Hibernation
2. Set Power Profile to High Performance
3. In settings Gaming disable all game functions (DVR, anything on) this is MS Gaming stuff you likely never will use on PC and it runs no matter what you are doing.
4. Download a program called O&O ShutUp10 from oo-software_com. This disables the behind the scenes Telemetry ( communications happening you didn't authorize or realize is happening, that is wasting your CPU cycles) Just let it change the recommended settings. None of this existed in Windows 7 because they didn't spy on you back then, so you don't need it now. I recommend disabling it and potentially regaining 5-15% of your CPU'S muscle to go back towards gaming. Plus the added benefit of keeping MS and any 3rd parties they let in on the information out of your business. On older CPU'S I have been amazed at how much more responsive overall the system is with this change alone.
5. Set any Anti-Virus software to it's game mode if it has one.