It's not an apples-to-apples comparison, but the Wii's CPU was 32-bit, 729 MHz, and single-core, and its GPU was a 243 MHz SoC. I briefly checked the Samsung Galaxy S lineup as a point of comparison, and it seems like the second one (from 2011) already smoked those specs. As for space, even without doing any modifications to the phone it's already about half the volume of this mini-Wii.

Of course that's really just sidestepping the challenge of "how small can you get an actual Wii".

You could 100% make a smaller fake "wii" by emulating it with a smartphone SoC. Mid-range phones can emulate Wii and Gamecube at 2x resolution.

However, the intention of these miniature builds is to preserve the original device, just in tiny form. No emulation involved. As if it was an official product.

Well, the Wii GPU has 12 GFLOPS, while the Mali-G52 MP2 used in the Galaxy A14, the top selling Android phone of 2023, has 418.78 GFLOPS.

People have been running Dolphin on Nvidia Shields since the first one came out in 2015