Based on the specs you have shared, both the RX 6600 XT and the RTX 2060S/2070 would be good options for your needs. However, here are some factors to consider:
Performance: The RX 6600 XT is a newer card and has better raw performance than the RTX 2060S/2070. It also has more VRAM (8GB vs 6GB/8GB), which can be helpful for productivity tasks like video editing and programming.
Compatibility: Adobe Premiere Pro and Photoshop generally work well with both AMD and NVIDIA GPUs, but it's always a good idea to check their official system requirements to ensure compatibility.
Price: As you mentioned, the RX 6600 XT is cheaper than the RTX 2060S/2070. If budget is a concern, the RX 6600 XT would be a more cost-effective option.
Warranty: Since both cards are second-hand, it's important to check if they still have any remaining warranty left. This can be helpful in case there are any issues with the card.
Ultimately, if you prioritize performance and can afford the higher cost, the RTX 2060S/2070 would be a solid choice. However, if you're looking for a more budget-friendly option that still delivers good performance, the RX 6600 XT would be a great choice.