The standard display on the Apple II Plus was 40 columns, so applications developed for it will be displayed in 40 columns even if you selected 80 columns as your standard display by using the Control Panel Program.
There is a chip on the main circuit board that generates the characters that are displayed on the screen. The character generator on the Apple IIGS (and on the Apple IIc and later models of the Apple IIe) can generate 32 special characters little apples, check marks, checkerboards, and so on) in addition to standard characters like letters, numbers, and punctuation marks. The 32 special characters are called MouseText because they are used mostly in mouse-based applications.
Applications designed for earlier models of the Apple II won't take advantage of these special charactersat least not intentionally.
But you may notice little apples and check marks in place of uppercase inverse characters if you use older applications.
The original Apple II character generator ROM had two identical sets of uppercase inverse characters, one of which was unnecessary.
In the new character generator, the redundant set of uppercase inverse characters has been replaced with MouseText characters.
This doesn't have any effect on the way the application works, so if it doesn't bother you, go ahead and use the application. If it does bother you and you'd like an upgraded version of the application, see your authorized Apple dealer or contact the developer of the application.