How many FPS do Intel Core i9-9900K and NVIDIA GTX 1660 Ti manage in Counter-Strike 2 at 1440p and high settings?
An estimated 61 FPS in Counter-Strike 2 at 1440p and high settings. In more demanding titles such as Cyberpunk 2077 it is closer to 31 FPS. Both are model calculations, not measurements.
Is the Intel Core i9-9900K + NVIDIA GTX 1660 Ti combination enough for 1440p?
For 1440p this combination sits at the entry level. In demanding games you will need to reduce detail or use upscaling such as DLSS or FSR. Balanced for 1440p. The graphics card is the narrower side, and at this resolution that is how it should be: more pixels load the card, not the processor. Your processor keeps headroom (83 % apart), which is why the frame rate stays steady in busy scenes. Upgrading is an option, not a must. Around 61 frames is smooth.
Does one part hold back the others in Intel Core i9-9900K + NVIDIA GTX 1660 Ti?
Balanced for 1440p. The graphics card is the narrower side, and at this resolution that is how it should be: more pixels load the card, not the processor. Your processor keeps headroom (83 % apart), which is why the frame rate stays steady in busy scenes. Upgrading is an option, not a must. Around 61 frames is smooth.
Is an upgrade worth it?
The next step that makes sense by the model would be AMD RX Vega 56. Concrete suggestions with price and cost per FPS come from the buying advice in the Performance Hub.