The motherboard itself, the memory speed and size, the type of USB ports (there have been reports about problematic USB chip sets), the type and size of the SSD and so on.
The CPU is just the processing piece, which is as fast as the surrounding equipment.
Start searching the forum and you find lots of tips and stories from other users and what they have done. Even with a 9th generation CPU it seems to be possible to have a great system
And btw. there is still the workaround to disable the E-cores in case they cause problems or go for AMD CPUs. I still don’t get it why everybody seems to believe only Intel is able to build processors.