There’s a smoothness to the way that the Gnome 3 customisation options are operated in Ubuntu. Once you are in the Appearance settings dialog, some of the (clearly worded) options lead to other dialogs. However, by the standards of a typical Linux desktop, the options for customisation are somewhat limited in Ubuntu. In particular, there is no easy way of making detailed font selections or customising the theme.
Pop!_OS, although aimed at power users, doesn’t improve on what Ubuntu offers in this department. The Appearance options, for example, simply enable the user to select from the Light or Dark theme. As with Ubuntu, it’s possible that these simplified options might be less comprehensive than what switchers are used to. If there is an element that the user can’t live with, they might have to dive deep into editing files or adding extensions to change it.
While a little more complicated to customise, Mint’s Cinnamon desktop comes with an extensive set of tools for modifying the look and behaviour of the desktop, making it closer to a traditional Linux desktop in that regard.
Linux Lite relies on Xfce’s customisation tools, delivering a good balance between discoverability of settings and full control over how everything looks and works. Of the two, Cinnamon’s dialogs are perhaps a bit more polished.
MX Linux has a lot of scope for customisation, but uses a mix of its own and Xfce’s tools. Nearly everything can be changed, but it’s more complicated to find the right tool to use, and there’s a possibility of overlap between different areas of the settings.