It will be used for mining also.
My plan of this setup is.
MSI B450 Tomahawk max motherboard
2x3600mhz ram
2xRX5700
Ryzen 9 3900x
So not to waste other hardware i can do dual mining for example with GPU i mine ETH.
Also can use it as gaming and rendering bench.
In such a way you are getting not a rig but a serious worstation that you can use in any way: for games, for mining, for work. If you will use it only for mining ROI would be really huge. Its nice decision.