I have a Ryzen 3 2200G APU with an integrated Vega 8 GPU. Ryzen Master sets my GPU "GFX" 400htz when it's supposed to support 1.1Gtz. when I turn up the GFX pretty much at all it usually runs stable but at some points it goes from like 34fps suddenly to 14fps then back again over and over again.
Hi, it's probably thermal throttling, check your CPU temps with a software like CPUID HWMonitor, ThrottleStop or etc. If it reaches 80+, consider cooling solutions like laptop cooler, Fresh thermal paste or etc.
Found out it was both not enough voltage and too high of temp. Was getting 80-85 c. I lowered to 900MHz with a little more voltage and is stable but still temps are around 75-78 at full load. I got an aftermarket cooler (Gammax 200t) and will install tomorrow. Other people say that cooler on their 2200G builds lowered their temps from 70-80s to 40-60 c even with overclocks.
Your CPU is 65 watt, that cooler can handle up to 100 watts. It's more than enough for stock and some modest overclock. Also, consider adding some cheap fans if you have enough space, as they help circulate air. If you do, make sure you don't mix up intake and exhaust.