Would recommend getting a B450 board over either of those, even the cheapest B450 board is fine, but don't get A320, it's for OEM build for people who can't build their own PC's.
If you insist on A320, then the only compatibility criteria is that the board should have an updated BIOS that supports 2nd gen Ryzen CPU's. Ask the retailer whether it has updated BIOS or not, and if not, you could ask him to update it for you. If it is updated, then the board should work with the R5 2600. If you can buy those parts though, I think you can afford a B450 board as well, it's a waste of money to buy A320 for a performance-oriented PC.