The text under the toolbar buttons can be hidden by unchecking Show Toolbar Text Labels. The text under the graph buttons can be hidden by unchecking Show Graph Button Text Labels. The grid on the measurement thumbnails can be turned off by unchecking Show Grid on Thumbnails. Animate Task Panes controls whether the task panes (Target Settings etc) slide open and closed. General Font Size is the base font size (in points) for REW. Graph Font Size is the font size used for the graph axes. Font size changes do not take effect until REW is next started.
The Prevent Multiple REW Instances option stops multiple instances of REW from running, which can occur if REW is started up without shutting down an existing instance or, under Windows, if an REW .mdat or .req file is double-clicked when REW is already running. If this option is selected and a new instance starts up, it passes any files it was opening to the existing instance and shuts down. Close all instances and restart REW to apply this. N.B. to implement this feature the first REW instance starts a local socket server which listens for other local REW instances starting up. This may generate a firewall warning message on startup asking whether to block or allow the local port server, select "Allow" to use this feature. This option is not required under OS X and does not appear.
Suppress Soundcard Errors stops REW showing an error message if it cannot access a soundcard on startup, this may be used if REW is being used to analyse measurements on a computer without the audio interfaces needed for making measurements.
If Confirm Unsaved Measurement Removal is checked REW will ask for confirmation if you try to remove a measurement that has not been saved since it was last modified. This setting can also be changed from the removal confirmation dialog.
Under OS X Use OS X-style File Dialogs changes the file selection dialog to a format more like the native OS X file chooser, but note that the OS X-style chooser does not have the preview panel which REW uses to show the contents of mdat, req, calibration data and image files.