[wareck]

dedup it's not only files, but stucture of file
for example, a .zip file full of GIFs.
Each GIF file will start the same (header), and dedup will also take this into account to reduce the final size.

Precompression => yes decompress file and some kind of file (gif, png ,mp3) to let them compressed later with a better compression system

Chunks/dictionary and depth :
They will impact performances (better speed, better compression, better detection)
these values are a compromise between performance and speed.
values that are too high can also lead to CRC errors.
like dictionary, it's a way to reduce a file size if inside they is several time the same words, same structure, or same hex data
depth is to find stream deeper inside file
like if you have a zip file with inside a movie with a wav file. depth 0 => zip file , depth1 =>zip file with something inside=>movie , depth3 => zip file with something inside=>movie => wav
but with a high depth, soft may need to read file several times => more time to compress/uncompress
also going deep may add some errors and you will have CRC error during decompression
again => these values are a compromise between performance and speed.

streams...
They are in files
For example, to put it simply, a large game file can contain images, sound, texture, text...
during the analysis process, software can indentify a sound stream and decode/decompress/recompress

diskspangui is a compressor, but to be fair, is a collection of diffèrent programs
in the same file you can have several type of data

like if you mix oil and vinegar to make a salad sauce
then you want to put back oil and vinegar in their bottle
you wll need a tool to separate them and work on them each on their own.

diskspangui it's a GUI for several freearc function.
you can open files with freearc (not to unpack, just read them, if you want to unpack, you will need to add soft/config in freearc software)