Speaking of visualization...that last figure in this post is super interesting in part because you can actually see some of the redundancy in the base64 encoding on the left, in the patterns of vertical lines.
In general, better compression means output that looks more like "randomness"—any redundancy implies there was room for more compression—and that figure makes this quite clear visually!
Yes, the data is the bytes 00, 01, …, FF repeating, and that pattern is highly visible with a power-of-2 encodings, but not visible with other bases (for similar reasons that 0.1 as a (binary) float doesn’t behave as people expect).
In general, better compression means output that looks more like "randomness"—any redundancy implies there was room for more compression—and that figure makes this quite clear visually!