Couple pieces of information coming from JZ on HardwareLuxx Forum:
1. ACPI S3 does not work with Renoir on either A300 or X300. S3 is "Suspend to RAM", aka "Sleep" in Windows (as opposed to S4 "Suspend to Disk" aka "Hibernate". This will likely never be fixed for A300 and is pending investigation between ASrock and AMD for X300
2. A new (newer than O) ComboPI V2 BIOS is in the works for A300 that brings back AMD CBS/PBS menus that are currently not available in the ComboPI V2 Beta BIOSes.
Meanwhile, ASRock Japan Official Twitter says, paraphrasing here, "X300 uses same PSU as A300 because that is 180W and that is plenty":
We know that is not true - A300 has 120W PSU. JZ has confirmed X300 uses the same PSU. I am still amazed here. From the couple reviews I read an OC 4750G alone can pull upwards of 120W with no other system component involved at all. For ASRock to not update the power solution appears... absurd?
Power bricks are rated for sustained output, so I guess it might be 180W peak? That makes it sound like a relatively low quality brick though. Might also just be a brain fart.