I don’t have a horse in the race and I’m speaking from ignorance, but I noticed that Valve’s offering only requires 300W of power. That sounds very appealing for the sort of games I play.
Would it be difficult to make a PC with a similar power/performance profile?
Note that the power estimate for the build above is only 325W. The power supply is beefier than that for headroom and economics.
It wouldn't be surprising if Valve's efforts at integrating the unit (putting the relevant chips on a single board, eliminating anything unnecessary, and improving cooling) could shave a significant amount of power.
Impossible because of the unified CPU/GPU chip that the Steamdeck used.