How many megapixels does the GH5 use to generate a 4K video? Does it downsample from 20 megapixels to 8 megapixels, or does it use the full 20 megapixels for 4K?
4k is approximately equal to 8 megapixels. 4k is 3840 x 2160 pixels, or 8,294,400. 8 megapixels is technically 2^23 = 8,388,608.
The GH5 uses the full sensor width, and downsamples to 4k. It does not use the full sensor height, unless you're in anamorphic mode, and therefore it isn't downsamping from 20 megapixels. The sensor width is 5,184 pixels, so the height for a 16:9 aspect ratio would be 2,916 pixels and the total number of pixels from which it is downsampling would be 15,116,544.
