Don’t do it.
The third PCIe slot won’t work.
The plan in my PC Build was to have an x16 slot for the H700 RAID card, the x4 for the Asus 10Gigabit network adaptor, and a PCIe to U2 SSD card (plus U2 SSD) to act as the cache within a VM.
The issue is that the 3400G only supports 2 PCIe lanes, 1x x16 and 1x x4. According to the manual, you can split the x16 into 2x 8x’s but the option just isn’t there in my BIOS. I’ve tried updating and downgrading the BIOS, logging a case with ASRock (no response as of yet) so I’m forced to conclude that it does not work. This was echoed by a user in the Reddit Homelab discord who had the same issue with the same motherboard/CPU combo. He fixed it by upgrading to a Ryzen 7 3700X, however, this isn’t an option for me as the 3400G uses onboard graphics and other processors of a higher spec do not. EDIT DEC 2021: So the board has a basic GPU onboard meaning that processors without an iGPU will work in this board and you will have a video output. I wasn’t aware this was a feature on motherboards to have an onboard GPU, so I’ve learned something there. I’m now running a Ryzen 7 3700X.
Partially my fault for not checking, but honestly, it’s something I thought I wouldn’t really need to worry about.