Why is my new PC struggling in some games?

At 1440p with Epic settings, the graphics card is the likely limit, not the CPU. Try 1920×1080 and a High or Medium preset, then compare performance in the same scene. If the frame rate improves a lot, that points toward graphics settings or GPU capacity rather than a basic setup fault.

Before changing parts, check what is actually happening while the game runs. Use a monitoring tool to look at GPU and CPU usage, temperatures, clock speeds, and memory use. Also note whether the low FPS happens everywhere or only in that boss fight. A repeatable test with the same settings will tell you more than judging from one intense moment.

Check the basics too: install the current graphics driver, make sure the game is using the discrete GPU, and confirm the display cable is connected to the graphics card. Since you’ve already checked the cable, I’d focus on drivers and in-game settings next. Frame generation can help smooth output if the game supports it, but test ordinary rendering first so you know the baseline.

The CPU is much stronger than the GPU, but that mismatch doesn’t by itself explain a sudden 16 FPS result. The 16 GB version of the card gives you more room for high-resolution textures than an 8 GB model, though it still may not hold Epic settings at 1440p in every demanding game. Lower the settings that hit the GPU hardest, especially resolution scaling and effects, and see whether performance becomes stable.