The DeskMini A300 was quite tempting for me too.
For the DeskMini A300, the restrictions I've noticed are:
- SODIMM RAM.
- Can't overclock CPU/iGPU.
- M.2 slots on paper look like they only support NVMe SSDs (not SATA ones). But there are two SATA ports for 2.5" SATA SSD anyway.
In my opinion, if you're going for a Ryzen APU it's because you want a small case like the In-Win Chopin or smaller (e.g. DeskMini A300, etc). If you're going for a bigger case than that (e.g. SFX PSU, room for dedicated GPU) then R5 3600 or R5 2600 are going to give you far better performance.
Therefore, out of your above choices, I'd choose the DeskMini A300 option.