Beelink EQR6 has an internal PSU and is also quite small, a bit smaller in footprint actually. It even comes with two full-size m.2 slots and expandable RAM.

Mini is great, exceptionally so, I actually just got a rather souped-up one (that's the reason I'm in this thread) but x86 vendors are catching up and there's a certain possibility that more established brands will pick up.

An external power adapter means a DC power input, which can be upgraded with a LiIon battery. It’s more expensive to do for AC.

That’s a very nice upgrade in many places, and for many scenarios. A power brick, meanwhile, is easy to hide out of sight.