If I wanted to make the most portable most powerful system then I'd add a Sonnet Puck eGPU to the Minisforum X35G.
The X35G is 136×121×39 mm, can be powered from USB C and has TB3. The Solo can provide 60W to the host so one brick could drive both. It's 152 x 130 x 51mm so you could stack them. Of course the brick is huge. But I think this wins the size/performance competition.