nvidia 3060 ,3060ti or 4060,which is better

I want to upgrade my GPU. My main purpose is training deep learning models and playing AAA titles (like RDR2).

Which one should I choose among these three options?

RTX 4060 has fewer CUDA cores and less VRAM compared to the RTX 3060. RTX 3060 Ti has better raw performance than both.

I have an HP 22fw 75Hz monitor and an Antec CSK 550W PSU.

If I go for the RTX 3060 Ti, will I need to upgrade my PSU to 650W?

Note: I am looking to buy a second-hand GPU.