How Do I Do A Search For Only Mission-Produced Light Curves, Only QLP Light Curves, Or Both?

In Portal

Mission = "TESS" for mission-produced light curves, "HLSP" for High Level Science Products.  If you want to only include official, mission-produced data, and exclude all HLSP products, set MISSION = "TESS".

Project = "TESS" can be used to find any TESS-related products.  This includes official, mission-produced data AND High Level Science Products that are derived from or relate to TESS data.  If you want the broadest possible search for "anything related to TESS", set PROJECT = "TESS".

Provenance = "QLP" can be used to find any QLP light curves.  This will exclude all official, mission-produced light curves, and any other HLSP that are not from the "QLP" HLSP.  Each HLSP has the Provenance name set to their HLSP shortname, and of course you can include more than one in a given search.

In API / astroquery.mast

These same columns are available when searching through the MAST API and astroquery.mast.  The only differece is that the fields are named differently in the query calls than they are in the Portal.  "Mission" is "obs_collection", "Project" is "project", and "Provenance" is "provenance_name".

Can I Filter Out (Mission, HLSP, Specific HLSP) Light Curves Before A Search Using Portal?

Yes you can!  You can apply filters to include or exclude Mission, Project, and/or Provenance values before or after a search.  After a search, these columns are available on the left-side panel to be able to apply further selections after your search.  If you want to apply these conditions BEFORE doing a search in Portal, you will use the Advanced Search link located below the target search box.  You can then apply conditions based on these and other columns before doing a search.  You can do a search without a coordinate (a pure "metadata" search), or you can include a resolvable target name or valid coordinate and search radius using the "Object Name or Position" box.  Regardless, your query can not exceed 50,000 return rows if you want to load them into the Portal to download products.

Location of Advanced Search In Portal