Well, I can tell you what I do...
To use the editors to their fully potential, you really need to know/look into the game xml files.
Then when you are quite familiar with some basic structure for say the techtree or a planetimprovement, you can start a mod...
Lets say you want to create a custom race techtree...
Best would be to copy an existing techtree and alter it.
If you go for copying, you first need to alter all the tech id of some/all existing techs by hand, depending on how many unique tech you want to have. The SD Techeditor doesn't support tech renaming, unless you got some other tech editor
After you done that, you can start the techtree editor, and alter all your 'new' techs.
You can also do this step by step, branch by branch.
As for the PI, you better completely design them with the editor, and then just copy sy some galactic achivements/superprojects.
Same applies for the shipcomponents.
One thing said, the stardock editors don't like xml comments that much and delete them!
If you want an example TA mod, try my Custom Race mod in the library.
Basically, it is a constant switching for me between some different editors and visual studio.
Hope that help a bit.
