I would also think that AMX is much simpler to implement — it's a very straightforward device with a simple ISA. I'm wondering how it will be with SVE/SVE2 (but then again ARM has it in A510...)
Oh, of course. It's just that E-cores offer some additional throughput — 20-25% is nothing to sneeze about.
One thing does not exclude the other. Just because crypto mining is a large environmental problem does not justify increasing energy cost of running consumer PC hardware. Personally, I don't much care about the enthusiast-class hardware, that's niche enough, but the increased power consumption also does affect middle-class and these things add up.