DLLs/sqlite3.dll 557K
This is sqlite3 itself. I am presuming that the phrase "replace the sqlite DLL" above refers to this one
Correct.
-- although the same argument actually holds for the .pyd file
Not quite. You can download Windows binaries for newer sqlite versions from sqlite.org, so you don't need a compiler to update sqlite (which you likely would if _sqlite3.pyd would need to be replaced). So you can "bypass" Python and its release process for updates to sqlite.
libs/_sqlite3.lib 2K
I think this is a summary of the entry points into one of the above DLLs for the benefit of other code wanting to link against it, but I'm not sure.
Correct. I don't know why I include them in the MSI - they are there because they were also shipped with the Wise installer. I see no use - nobody should be linking against an extension module.
I do not know whether upgrades (like 3.0.0 to 3.0.1) would clobber other things added here.
It would, but not in a harmful way.
If the user had upgrade sqlite, upgrading Python would undo that, though. So one would have to re-upgrade sqlite afterwards. Regards, Martin