Correct.
These days, a processor slower than 2.1Ghz is a low-end model most likely in a computer that will also have cut other corners to hold the price down and will therefore be a poor performer in general. I think the Help pages are trying to steer SketchUp users away from such models, but I don’t think they meant to imply that a faster clock speed won’t yield better performance.
The difficulty for non-techies is that there are a lot of factors that the engineers can trade off when designing a computer, and comparisons based on specs such as CPU clock speed can be misleading. For example, the 2.6Ghz i7-9750H used in the base model of the new 16" MBP benchmarks as 3% slower than the 2.3Ghz i9 used in the next configuration step up. But that’s also so small a difference that you are not likely to notice it during use. The greater difference is that the i7 is a 6-core version whereas the i9 is an 8-core version - which as we have discussed does not matter to SketchUp.
My general advice would be that unless your old computer is at least 3 years old you are not likely to notice much difference when upgrading to a new one of the same kind. If you have a top-end iMac or MBP, “upgrading” to the newest one is likely to disappoint you. The changes these days are more incremental than radical in the kinds of CPUs used in consumer computers.
This is again a uni-directional recommendation based on the fact that less than 1GB of dedicated graphics memory suggests an older or cheaper graphics system. Somewhat more (e.g. 2-4GB) is almost certain to also involve a more capable graphics processor, but going further is not likely to make much difference for SketchUp. For the same reason, high-end “gamer” graphics do not provide much advantage to SketchUp. It simply doesn’t use the features they add.
So-called “integrated graphics” (which includes all of Intel’s offerings such as the UHD 630 you mention) put the graphic circuitry on the same chip as the CPU and use the same RAM memory as the CPU. They aren’t a graphic card and don’t have RAM of their own. On Windows, these are notorious for issues with OpenGL support in their drivers. Because Apple writes their own drivers, there are usually not issues there. (Aside: contract issues with Apple writing drivers is reportedly one of the reasons Apple parted ways with Nvidia).
Yes indeed!