Multiple GPUs?

I’ve read that CPUs have PCIe lanes and that those are used by the graphics card.

1.- So if a processor has 20 PCIe lanes, does that mean I can only have one x16 (or 2 x8) graphics card?

2.- Does that mean if I want two x16 I need a 40 PCIe lanes processor?

3.- If that’s the case, why does having multiple graphics cards on a 20 PCIe lane processor actually makes a difference while GPU rendering?

(About the third question, here’s a post showcasing it)

https://www.cgdirector.com/best-har…-redshift-vray/

4.- If it doesn’t affect negatively having multiple graphics cards on a 20 PCIe lane processor while doing GPU rendering, then, when does it actually matter? (negatively)

Thank you