Rotation, resolution, overscan, audio and video output, and the advanced switches. Which settings exist depends on the device.
Settings live on the screen itself, on its Settings tab, and apply to that screen only. Save at the bottom.
Which settings you see depends on the device. A Raspberry Pi based screen has the most, a Player Max has fewer because it needs fewer, and a Screenly Anywhere screen has only the two that a browser or an app can control.
Rotation, resolution, overscan and object fit: the settings that decide how your content sits on the panel.
Sending video over HDMI or composite, and sound over HDMI or the 3.5 mm jack.
The low-level HDMI controls on Raspberry Pi based screens: what each one is for, and why you should not touch them unless a display is misbehaving.
Two switches on ScreenlyOS screens: certificate verification, and exposing device metrics for your own monitoring.