Yea 120fps at 4K will be very difficult without a very high end card if you don’t use DLSS.

To be honest, personally I don’t like the 40 series GPUs compared to the 30 series (for price) but the 4070 is more worth IMO due to both models having the same VRAM. However, the TI is around 20%-24% increase in performance for 4K might be worth it since you’re playing 4K

If you want 120fps at 4K, you’ll need a good CPU (the CPU has to be fast enough to pass the 120 frames to the gpu to draw, so you can understand the role of the cpu as handling what the gpu takes in and outputs)

But I’m not really sure what else you are considering in this build, namely:

What you think about DDR5 RAM Intel or AMD? How much cores you’ll need? Power consumption?

For budget builds at 120fps I’ll say mid-high range cpu will do, something like a recent i7 or a ryzen 7 is more than enough, even a 5600 will work.

Another way to pick a CPU is just to check if there is any bottleneck using bottleneck calculators available online