Compression & Generation of Indexes

Hi,

I am working on compressing some InfoCubes that have never been compressed before. I am creating a process chain that starts the compression job weekly.

It would be a great help if someone can answer these questions -

1. Should I delete and create index before I start the compression step in the process chain? Or is it more beneficial if I do the deletion of index before the compression step and creation of index subsequently after the compression step. I am not sure whether the indexing works on the F table or the E table, that's the reason for this question.
2. In the process chain steps 'Delete index' and 'Create index', I see an option to choose 'Infocube', 'DTP' and "Execute InfoPackage'. I understand the 'InfoCube' part but why are 'DTP' and 'InfoPackage' options here and in which scenarios does it make sense to choose these options.
3. Similary, in the process chain step 'Compression of the InfoCube', I see an option to choose 'Delete Index', 'DTP' and 'Execute InfoPackage'. How are these options useful?