No, you're not experiencing thermal throttling.
No, you're not experiencing thermal throttling.
I'm also experiencing occasional drops of 10-15 fps across all games when using identical settings and locations.
It's likely your CPU is running around 3.9-4Ghz thanks to the boosters at 4300-4350Mhz. As it gets hotter while under load, cooling it down further will increase clock speeds and reduce performance drops. You might see about a 10% drop in CPU speed from being warm during heavy use (adjusting by 1-2% for other factors).
Consider a reliable brand like Noctua or Arctic Cooler for high-quality air coolers.