If you want to overclock, then it can't be an a320 chipset. I would definitely suggest you get a b350 based mobo, because the 2200g comes seriously underclocked by default. From what I've read (and I researched it quite thoroughly) the 2200g can easily and safely be OC'd to a higher spec than the vanilla 2400g, provided you have a b350 based mobo. On the other hand, the 2400g can only be overclocked moderately without risking severe stability problems (I speak from experience). As to which exact b350 mobo, I can't help. I have the Asus B350M-A, but with 2400g - I get blue screened rather easily if I try to push the clocks.
As to whether you you'll need a BIOS update to use the Ryzen APU, I think that will vary from vendor to vendor. You need to communicate to the vendor that you will be running a 2nd gen Ryzen BEFORE you buy (personal experience again). I had to send my board back to the vendor for a BIOS upgrade, which they did for free, but that added three weeks to the build time
Don't buy from a vendor who won't pre-install (and test) the required BIOS before shipping!
Oh, BTW, I think your 2666mhz memory will only run at 2133 on an A320. Even on a b350 you have to go into the BIOS to get RAM to run faster than 2133, and I don't think there's even the option to change mem clock on a320 mobos.