RPi5 is far from low power these days.

But a lot closer than anything from Intel (except a few Celeron-style chips that are even slower).

The Intel Celeron mini PCs you decided to exclude because they don't fit your narrative, actually use less power at full clock and idle at the same power consumption.

They're slightly slower at peak, but they're also a much fuller package with SSD interface, Intel graphics with multiple monitor support and no need for running custom linux distros due to x86.