The vulnerabilities have absolutely nothing to do with the SATA/AHCI or chipset drivers; there won't be any changes to them as a result of the vulnerability remediation.
The chipset drivers are part of the base O/S. The Chipset Software package does not actually install any device drivers. instead, it provides .INF files that configure the built-in, Microsoft-supplied drivers to optimally support the Intel chipset hardware. There are no changes to these INF files as a result of the vulnerability remediation.
The vulnerability remediation consists of changes to the processor microcode, which is (or will be) delivered within BIOS updates from you board/system manufacturer, and workarounds in the O/S to close the other portions of the vulnerabilities.
Hope this explains it,
Yes, that is correct. As you call down into Kernel space, it must now transition to a separate memory space and this is a more costly operation than it was with the shared memory space used previously. How much this will slow down your application depends upon the amount of time you spend making calls into the Kernel. For most applications, the cost is 6-7%. Benchmark applications, because of how they work, will suffer more.