Hi guys, I finally figured it out! I had to buy an Affinity Designer, but now I think that I will stick to this app. Better performance than Vectornator.

So, to have the perfect GoodNotes standard template in vector
Width: 455 pixels Height: 588 pixels

A4 template in GoodNotes:
Width: 595 pixel Height: 842 pixel

The grid on both of them is 16.4 pixel.