FF3usME is the most complete editor as far as game data goes. It can basically edit everything outside maps, levels, monster sprites, chests and portraits. Most general data can be edited with the latest version. Version 6.70 also has an option to expand some things, notably dialogue space and AI scripts space.
FF3usME is a C++ MFC application. It has been developed since the late 90's and last version was released in 2017. Its source code is not public which makes the application less flexible when you have data expanded or relocated. FF3usME has also been known to store application settings at the end of the event banks (end of bank $CC). This has a result of overwriting any event you put there each time you save with the application.
The editor is still slowly in development and it pass the test of time as the premium editor for FF3us 1.0 and 1.1.