X_Splinter

Id suggest going for a barebones like deskmini x300 then adding the cpu, rams, and storage. Heck you can even buy them prebuilt with all the parts included tho i wouldnt trust that since they prob cheap out on ram which is a horrible thing
 
Deskmini x300 formfactor is mini stx which is abit smaller than mini itx, for the parts buy a 3200g, 8x2 3200mhz sodimm rams, and a cheap m.2 like kingston a2000

Im glad the flashback worked! Hopefully when other people have this same issue the flashback option works for them as a corrupted BIOS is such a crappy experience.

I hesitate to suggest this but seeing as this b550 has a bios flash button, barring anyone else having a better idea you could download a clean, full bios firmware on a usb and use the bios flashback to try to resolve the issue. AGAIN TRY AS A LAST RESORT, and dont turn it off yet as the bios may become corrupted. Hopefully someone else here has had the same exact issue.
 
How to bios flashback asus mobos: https://www.asus.com/support/FAQ/1038568/

PCPartPicker Part List
CPU: AMD Ryzen 3 2200G 3.5 GHz Quad-Core Processor  (€96.00 @ Amazon France) 
Motherboard: MSI B450M PRO-VDH MAX Micro ATX AM4 Motherboard  (€74.90 @ Amazon France) 
Memory: Patriot Viper 4 16 GB (2 x 8 GB) DDR4-3000 Memory  (€64.98 @ Amazon France) 
Storage: TCSunBow X3 240 GB 2.5" Solid State Drive  (€26.99 @ Amazon France) 
Case: Cooler Master MasterBox Lite 3 MicroATX Mini Tower Case  (€35.92 @ Amazon France) 
Power Supply: be quiet! System Power 9 400 W 80+ Bronze Certified ATX Power Supply  (€44.37 @ Amazon France) 
Total: €343.16
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-11-19 13:55 CET+0100
 
better in most regards. and you avoid the Mobo that is fairly bad QC on. 
 
edit: changed the case, didnt notice the first one didnt have a fan. 

You dont have to rename the SSD to D: even, though it will break the shortcuts linked to files that were in the HDD.
 
Otherwise, it's just copy and paste. No need to be as complex as boot drive swap

Alright, so what you will need to do is go download DDU, LINK HERE Follow the instructions, then go re-download the drivers from nvidia's website. This will resolve your problem. 

if you can afford it i would get noctua nf-a14's

If your concerned aboy noise.It's most likely coming from the pump,otherwise get a pair of ML fans or be quiet ones

I did a clean install of GTX1070 drivers, updated the MSI Gaming APP and updated the BIOS.
 
I have played twice and no crashes... I hope they wont come back

Confirmed... Got my replacement motherboard and now everything is working...
 
And what an awesome machine...

Confirmed... Got my replacement motherboard and now everything is working...
 
And what an awesome machine...

Damn i know that feeling OP, its always nerve wracking building the first fairly expensive build

please keep us updated for sharing knowledge, good luck

Looks really good to me but consider getting a 120hz or 144 hz monitor (1080p) because the 1070 can easily handle more games at those frame rates.