The FAA and Transport Canada recognize only the LPV approach as a "precision" approach.
LNAV and LNAV/VNAV are considered "non precision" approaches.
No, an LPV is not considered a precision approach.
LPV and LNAV/VNAV are considered Approach with Vertical Guidance (APV). APV minima depict DA(H).
LNAV is considered a Non-Precision approach (NPA). NPA minima depict MDA(H).
One does not "add" anything to an LPV or LNAV/VNAV procedure to "change it" into a DA. The DA is determined by obstruction clearance standards.
For definitions, ref: AIM 5-4-5, FAA Order 8260.3B, Transport Canada AC 700-023, and ICAO Annex 10.
Or see some discussion earlier in the thread.