First time I build a system and I have to say the following:
A great motherboard, everything you expect to see in a budget motherboard. Now, regarding the bios, which many people in the comments say is not good, I have to say that it is quite decent and comprehensive. Now, if someone wants to have frills and fancy features in the bios or wants the bios to hold their hand to the point of absurdity in order to consider it good, sorry but they should probably be in a daycare center and not criticizing such a motherboard. The system I built is as follows:
Motherboard: Asrock B450M-Pro4
CPU: AMD R5 1600 3.2Ghz
RAM: 2dimm Kingston HyperX Predator 8GB DDR4-3000MHz (HX430C15PB3/8) (meaning a total of 16GB)
GPU: MSI GeForce GT710 1GB LP (temporarily until I install a better one, specifically the MSI GeForce GTX 1650 Super 4GB Ventus XS OC or the Gigabyte GeForce GTX 1650 Super 4GB Windforce OC)
PSU: Corsair VS 450 White
HDD: Seagate Barracuda 1TB (2.5") 5400rpm 128mb cache
Case: Aerocool QS-240
Additionally, I added a mini speaker to monitor everything in general (bios, RAM, etc.).
After setting it up and connecting everything properly, it wouldn't turn on (due to my mistake, read on to understand). Meaning, the fans would start working, then the message "No input signal" would appear on the screen, and after 20 to 30 seconds, it would shut down and the same thing would happen again. After trying various things, such as checking if the RAM slots were the issue, if the RAM was faulty (initially I had bought the G.Skill RipjawsV 16GB DDR4-3200MHz (F4-3200C16D-16GVKB) which were not on the motherboard's QVL, so I changed them to the ones mentioned above (which are on the QVL)), if the slot where I inserted the graphics card was the problem, if using the HDMI instead of the VGA from the GPU would make a difference, or if there was any loose cable. Finally, I took it to a technician who told me that I had bent all the pins of the processor when I installed it (a big mistake on my part, I didn't expect to cause such damage). Nevertheless, he fixed it and I have had the system for a week and a half now, and it works flawlessly, even with the GPU I mentioned at the beginning. The XMP on the RAM was enabled without any issues. It is important to note that I installed Windows 7 Pro x64 using Gigabyte's tool instead of Asrock's because I was having issues with it. In order to update your Windows 7 without receiving the "Unsupported Hardware" message, you need to install the "wufuc" tool (search it on Google and you will understand what I mean). Furthermore, when updating with Windows Update, make the updates one by one and NOT all at once (first ONLY the 2010 updates, reboot, then ONLY the 2011 updates, reboot, and so on until 2019). I say this because when I did it all at once, it caused my PC to reboot and go straight to startup repair, which couldn't perform auto repair and happened every time I turned on the PC. Using the Gigabyte tool on the USB stick (since the original DVD didn't work with the keyboard and mouse), I restored to the point before the updates and then, as mentioned before, I did them one by one and it worked fine, just took a bit longer. This way, you can have Windows 7 and avoid Windows 10, which has so many issues due to automatic updates, instability, security problems, etc. And if anyone disagrees, especially regarding security, I inform you that in Windows 10, having support and Defender doesn't save you from anything, and in Windows 7, now that support is ending, I have already installed Kaspersky Internet Security Free (a well-known and top antivirus) and I plan to get a license to be covered, so no problem.
Edit: I forgot to mention that my motherboard came with BIOS version 3.60 and it works fine with the R5 1600 (I don't know why Asrock says it's not recommended to update the BIOS with the summit CPU, which is the R5 1600, meaning mine). The RAM at 3000MHz (to be precise, 2933MHz) gave me bluescreens. I set them to auto, which is 2400MHz, and they work fine. I have now set them to 2667MHz and I will update you later.
Edit2: Finally, the RAM at 2667MHz works fine, so it is also the maximum I can consistently use (after all, according to AMD, the R5 1600 supports RAM up to 2667MHz, so it's logical for this to happen).