'Appearance' should offer visible examples for every setting, as they change

(Windows 10 Chrome browser) I can barely see the example at the top when I change the “Message Display” from cozy to compact.  That shouldn't be a worry.

The appearance area should hover above the settings, and always stay visible.  Then when I change a value it should be obvious what they do.

I tried changing “Space Between Message Groups” and it did nothing in that box (after scrolling up).

Settings that alter visible results should be shown visually, and immediately, so the user knows if they want to keep that alteration.