XPS 8950, questions about possible new GPU

I have an XPS 8950 which came with an Nvidia RTX 3070 (8Gb video RAM).  My primary use of the computer is photography-related, processing images with Lightroom Classic and Photoshop.  I am thinking about replacing the RTX 3070 with a video card with more video RAM.  In particular both in terms of amount of video RAM and price, I am considering either the RTX 5070 (12Gb) or RTX 5070 Ti (16Gb). 

When I look on Amazon, Newegg and the Nvidia websites, I see these two cards that appear to be specifically for specific brands of computers, for example, ASUS.  But I don't see any for Dell.  Does this mean that neither of these cards are compatible with my XPS 8950 or wouldn't fit or would need connectors that my computer doesn't have, etc.?

If the RTX 5070 or 5070 Ti aren't compatible with the XPS 8950, what 12Gb or 16Gb cards would be compatible with my computer?

Thanks in advance for any suggestions.

David