So far, AMD doesn't do the p-core/e-core thing. All cores will have the same ISA. They have talked about a "compact" core which seems to be a tweaked process that shrinks the core and decreases peak clocks a bit, meant to cram more cores into one chip. If CPU designs were like software, you might think of this a bit like someone choosing compiler flags to optimize for size instead of absolute speed, but still compiling the same sources.

I'm not sure what footnotes the earlier poster meant. One might be that the AMD model numbering is a bit obscure. You need to look closely that you are getting a Zen 4 core in your Ryzen, with the same model line mixing different CPU and GPU architectures in different models. I don't know if there are programmer-visible differences in what AVX-512 means to AMD vs Intel...

No, AMD doesn't have E-Cores right now, but even when they do it won't ever crash: they have Zen4 as their P-Core and Zen4c as their E-Core. Both support exactly the same extensions.