Actually I don't really know if it's a drivers problem, so I'm sorry if a mod need to move this thread...
What is happening:
I have a Gigabyte GA-F2A88XN-WIFI which is the only AMD mini-ITX motherboard that I could found. It seems working fine.
I have a Sapphire RX470 nitro+ 8go and as long as I do not install any crimson everything is working fine (slow but fine).
Then I installed crimson and the PC randomly freeze (like a total freeze that need a hard reset).
I tried crimson 16.7.3 and 16.9.2 Hotfix but no difference, I have good performance overall but It's randomly freezing after I installed it.
When I say randomly I mean I can use it like 15min to 1h without any problem and it stop working for no reason.
I tried under heavy task and without and It does not change anything.
I don't know if it's a manufacture error from sapphire that the driver is enabling, if crimson is broken, if the motherboard does not support the extra energy asked from polaris card, or if my chipset/bios need a special driver to support the polaris card.
 I just have a new symptom: the screen goes black and after a few second the windows 10 loging screen show up. I could not reproduce this one, it still mostly freeze.
PS: the malware option will be tested soon by re-installing windows