I’ve never understood why the Full Service layout was never either completed and taken out of beta, or ripped out of the D|S4 code, months ago — the name alone has misled and confused many people, not all of them newcomers.
FWIW, the setup I use which gets sorta-maybe close to the D|S3 look is to switch Layout to City Limits and Style to Highway. You should also go into Edit>Preferences>Interface and check the tickboxes for Hide Lesson Strip and Orient Tabs Along Top. If you’ve “bought” the free D|S4 Pro then you’ll also have an installer for the Darkside setup, which was intended to give something close to the D|S3 look; I’ve never used it, because it isn’t close enough for me. Some people do prefer it, though. All this gives you something that still isn’t as compact and easy to use as D|S3, and I for one am still not quite happy with it, but I can use it.
One last point, if you’re getting tired of the glaring white “What Do I Do” pane in several tabs when nothing is selected, go into Customise Colors (same menu as the Style selection) and change the Lightest Color from bright white to a nice medium grey. Nothing else important uses this colour apart from the highlight on some buttons, so feel free to use a shade that doesn’t leap off the screen and masticate the backs of your eyeballs.