Optimized PCB traces (thickness (of the traces, proper amount of copper)?, proper trace lengths to comply with the standards?) for higher frequencies (DDR, PCIe etc etc.), to name a few. It's like it is refined for what Ryzen (Zen, Zen+, Zen 2, Zen 3) actually needs.Can you elaborate a little bit on what makes the B550 MBs better designed?
My Strix B450F-II can easily run my DDR4-3000 on XMP. My Crosshair VI Hero/Prime X370-Pro needs a little tweaking. Of course, the AGESA plays a role here too, but the B450F-II feels more stable.