As for whether or not the coil whine is affecting performance, I think it's the other way around. Coil whine occurs when inductors and other ICs involved in power delivery to the GPU core are not fitted with anti-vibration pads.
As power draw increases (when the card is working harder), the coil whine will become more noticeable. As FPS increases, the coil whine will be a higher pitch. If coil whine suddenly stops, I would blame drivers. It sounds like your card is ready to go, but isn't being told what to do. This could be because of an overheating CPU, outdated and unoptimized BIOS, faulty Windows installation, or (more than likely) faulty drivers.
I have an analogy for you. Let's relate coil whine in your graphics card to how heavily you breathe when working out. If you've been working out rather intensely, you're probably breathing pretty deeply. If you stop working out, your breathing will likely slow over time, right? Same thing here, only the inductors calm down in a fraction of a second instead of taking time to catch their breath. Coil whine is a byproduct of the card doing its job. If it suddenly stops, the card is likely no longer receiving instructions on what to do next. Again, this can be a CPU issue, an unoptimzed (outdated) BIOS issue, an issue with Windows itself, or an issue with drivers.
Let's start with BIOS since it's sometimes responsible for many issues with Ryzen systems.
The board could have shipped with the original BIOS (v1.0). Almost immediately after that BIOS was released, a new version was released. That new version (v1.1) said that it patched certain system stability issues. Version 1.2 was then released, further improving system stability and memory compatibility. Later, BIOS 7A34v13 updated faulty code within the CPU itself and brought more general improvements to the motherboard. 7A34v14 says it improved memory compatibility again. 7A34v15 says it fixed something with PCIe (the connection on your graphics card) and further improved memory compatibility.
I recommend jumping straight to version 7A34v15. It will include all the improvements from the previous versions as well. Here is the link to the BIOS updates for your board:
https://www.msi.com/Motherboard/support/B350-TOMAHAWK.html#down-bios
Now onto drivers. This is pretty simple as well. Steps below.
Update BIOS and check that the system is stable before installing new drivers.
1) Download new drivers from
http://support.amd.com/en-us/download but do not install them yet.
2) Download DDU from
http://www.guru3d.com/files-details/display-driver-uninstaller-download.html but do not run it yet.
3) Open the Start menu. Open the power menu. Hold Shift while you click Restart. You'll see a fullscreen menu with blue buttons. Troubleshoot>Advanced>Advanced Restart>Restart.
4) Safe Mode should be the 4th option at this screen. If 4 on the numpad is not working for you, try 4 on the number row above the letters.
5) Run DDU while in Safe Mode. Use it to remove all display drivers.
6) Restart normally.
7) Install the new drivers you downloaded earlier.
8) Restart to confirm registry changes. Changes will occur automatically thanks to a command set by the driver installation, you don't need to edit the registry.
9) Try gaming again and see if issues persist.