The m-SSD should be empty.
I stated the HTPC with the Pentium and them upgraded to the i5.
To run the HTPC you need just one PS. The second is spare.
I think for shipping: The more separately packed and not installed, the less can be broken during shipping.
Im my experiance todays Hardware is alway Plug'n Play and easy to install. Also mostly self-explanatory.
If you are interested in mainboard details, perhaps you take a look into this pdf: