Workflow | Graphics Card Selection

I had RTX 3060 with 6Gb in my laptop. It works but is slow. A 900 pixel image takes 10 minutes to redefine 4x.
I bought external GPU holder to fit RTX 3070 with 8GB and it was much faster. 1,5 minutes per image.
I also tried RTX 5070 Ti with 16 Gb, but it only improved 30% in speed in spite of a card that is supposed to be 100% faster, twice as fast, in games.

(50-series cards does not have Open CL anymore, is Gigapixel relying on open CL?
What factor should I look for to know what performs better? Tensor cores?)

Are AMD cards any good at running gigapixel? What card do you use?
Intel cards like the B580?

How long time to redefine a 900 pixel image at 4x for you?

Hey, I have a RX5600XT and it take hours to upscale a image from 2800x2100 to 5600 x4200pixels!!! I’m now looking at alternate card solutions and thinking Nvidia RTX 5060TI or RTX 5070 but have no idea which considering the later is £100 more expensive will it give a relative 20% increase in speed over the 5060 and is GPU RAM more important than raw horsepower? BTW, I’m running a AMD 5900X with 32Gb RAM, all answers/ solutions/ recommendations are very welcome