I know AMD iGPU's graphics performance is sensitive to the RAM you pair them with. The wrinkle here is I am limited to SO-DIMM's. What is the best option without breaking the bank.
Have you been to the Asrock support website? They list ram they've tested and approved. There are certainly newer rams out there that haven't been tested by them but would probably work. A quick peek at Newegg.com suggests $80 should be enough to get a 3200 16gb kit. Try to get the lowest Cas Latency you can afford. You should also check your bios version and update it from their website if necessary. A lot of bios updates relate to ram compatibility. Here's a link to the ASRock QVL memory compatibility list that they tested for your processor. There are some 3200 modules listed, though they may be older and unavailable now. https://www.asrock.com/nettop/AMD/DeskMini A300 Series/#Memory3
Have you been to the Asrock support website? They list ram they've tested and approved. There are certainly newer rams out there that haven't been tested by them but would probably work. A quick peek at Newegg.com suggests $80 should be enough to get a 3200 16gb kit. Try to get the lowest Cas Latency you can afford. You should also check your bios version and update it from their website if necessary. A lot of bios updates relate to ram compatibility. Here's a link to the ASRock QVL memory compatibility list that they tested for your processor. There are some 3200 modules listed, though they may be older and unavailable now. https://www.asrock.com/nettop/AMD/DeskMini A300 Series/#Memory3