As I understand and have experienced Precision Boost (original and 2) is a CPU function not a motherboard function. Your boost will depend on your PC configurations ability to provide adequate power, cooling and core utilization.
"It is useful to imagine these three limits —power, temperature, and utilization—as a triangle. For the sake of conversation, let’s call that the “reliability triangle.” To ensure your processor is reliable over the long haul, it makes sense that processors self-manage to stay inside the reliability triangle."
"Precision Boost allows an AMD Ryzen processor to dramatically increase clockspeeds when the CPU has electrical, thermal, and/or utilization headroom to spare. In other words: if the processor’s analysis of its own environment indicates that it can safely go faster… it will" Quotes from Understanding Precision Boost 2 in AMD SenseMI technology
IMHO always update the BIOS to the latest version available and with a Gigabyte X470 Aorus Ultra Gaming and a Ryzen 5 2600X with decent cooling you should get a maximum PBO2 all core ~4GHz and single core/light load ~4.3GHz on stock settings as PBO2 is enabled by default (**depending on CPU load and silicon lottery)
As far as tweaking and overclocking the Gigabyte X470 Aorus Ultra Gaming offers all the bells and whistles, it offers bclk overclocking, offset voltages and many AMD CBS options and features. Paired with a R5 2600x it should fly, enjoy!
