Record Video
Settings › Camera › Record Video sets resolution (such as 1080p or 4K) and frame rate (such as 30 or 60 fps). The screen also shows roughly how much storage a minute uses on your phone. 1080p at 30 fps suits most talking videos; 4K or 60 fps suits detail and fast motion.
Formats
Settings › Camera › Formats lets you choose High Efficiency (HEVC/HEIF, smaller files) or Most Compatible (H.264/JPEG, bigger files, works almost everywhere). High Efficiency is the default for most people.
Grid and level
Turn on Grid to help with framing. Newer iOS versions also have a Level option.
Lock Camera
On iPhones with several back lenses, the Camera app may switch lenses as you zoom or move. Lock Camera (under Record Video on supported models) stops automatic switching while recording.
Preserve Settings
Settings › Camera › Preserve Settings stops the Camera app resetting your mode and options every time you open it.