GPU for rendering pc

I have a friend from Brazil who is an architect that specializes in waterparks. Her current rendering pc is too old and not upgradable. So I am helping her to buy a new workstation for her work.

I'm pretty experienced with pc hardware but can't decide what will be best GPU wise.

GPU's are very expensive but Brazil is crazy expensive when it comes to hardware

With her budget she can either go for a RTX 3090 24gb or a RTX 4070 ti super 16gb. Both are similarly priced in Brazil.

The software she uses:

Blender Archicad SketchUp Unreal engine Autocad

So what would be better, the extra 8gb Vram of the 3090 or the extra performance of the 4070 ti super?

I'm not sure because I don't know what will happen when the Vram will be exceeded. Will it switch to normal ram or just not work at all?

Rest of the specs will be (feel free to also comment on this

AMD ryzen 7900 boxed B650 Pci-e 5.0 motherboard 2x32 gb DDR5 6000m/t 512gb OS nvme ssd for OS 2tb nvme ssd for storage Basic black ATX case with plenty case fans