Probably (it widely depends), it's very useful to increase core counts to about 8 cores in most cases. After that, the actual practical returns are greatly diminished. So, moving from 8 to 16 grants only 15-20% better performance, etc.
I would much rather take 8 cores with Zen 5 performance per clock and frequency of 8 GHz rather than 128 cores with Zen 1 performance per clock and (all-core) frequency of 3.8 GHz. In a vast majority of workloads, the former would outperform the latter.
Yes, but that's starting from 6 cores.
Because 2 cores are not enough even if they are Raptor Cove 6 GHz cores.