The BIOS updates which include AGESA firmware will be available for Asus AM4 motherboards based on X370, B350, and A320 chipsets and should be already available on the Asus website. Asus was quite keen to note that you can update your motherboard with EZ Flash 3, which is Asus' own in-BIOS flashing tool.
As you know, the first batch of AMD's Ryzen desktop CPUs with Radeon Vega Graphics include the Ryzen 3 2200G and the Ryzen 5 2400G, coming with Radeon Vega 8 and Radeon Vega 11 GPUs. Although both of these APUs are quad-core parts, the Ryzen 3 2200G lacks SMT, which leaves it with just four threads, while the Ryzen 5 2400G has SMT enabled, so it packs eight threads.
The Ryzen 5 2400G works at 3.6GHz base and 3.9GHz Turbo clocks and comes with Radeon Vega 11 GPU (11 CUs) with 704 Stream Processors and a GPU clock of 1250MHz. The Ryzen 3 2200G is clocked at 3.5GHz base and 3.7GHz Turbo clock and comes with Radeon Vega 8 GPU (8 CUs) with 512 Stream Processors and a GPU clock of 1100MHz.
You can check out the full list of Asus AM4 motherboards that have the BIOS update below and you can find detailed instructions over at Asus' dedicated page.