1. ArchiCAD is more about CPU more than GPU, and the more Cores the better. So the more cores and faster cores the better.
2. You should not omit the GPU, you will need it for driving the graphics, and if not found, it may be bottleneck your work.
3. I don't know who have a surface book
4. On my personal taste, I like graphical real state, I would go with 17".
5. If the need for a new laptop isn't that urget, I would wait for CES 2021, new laptops will be shown there, and it's expected that Ryzen 5000 for laptops will make it's debut ...
On the other hand if there isn't nothing interested for you, older models will get a price cut.
6. This page is a good guide to start with for choosing the appropiate settings
https://graphisoft.com/resources-and-support/system-requirements
A good friend of mine have once told me that I´m so brute that I´m capable of creating a GDL script capable of creating GDLs.