So, I'm planning on building a pc using ryzen 3600 and 16Gb 3200 cl16 ram, I may do some mild overclocking.
Should I go with a used Asus strix b350f or a brand new Asus prime b450 plus? they're about the same price
Go with the newer b450 chipset.
B450 has better CPU and RAM support than previous b350 chipset.
Some b450 (like that Asus) might need a BIOS update before you can install a Ryzen 3600 CPU.
I would got with the MSI b450 Tomahawk Max, which comes with support for Ryzen 3600 out the box.