Generally speaking, if you work in a job that requires lessor qualifications, you are still held to the same standards as you would be with your highest qualifications.
Position Statement from Texas BNE:
"RNs Functioning in LVN Positions/ RNs or LVNs Functioning in Unlicensed Positions
The Nursing Practice Act (NPA) and Board Rules do not preclude a RN from seeking employment in lower positions (such as LVN, unlicensed, or technical positions), with purportedly fewer responsibilities. The Board holds a licensed registered professional nurse, who is working in a lower level position, responsible and accountable to the level of education and competency of a RN. Likewise, a LVN working as an unlicensed person is responsible and accountable to the educational preparation and knowledge of a LVN."
In Texas, at least, the Board considers your professional responsibilities to be commensurate with your highest licensure, NOT the actual job you are doing. While it doesn't address NPs per se, the same obligation would seem to be inherent in the Board's position.
This is reinforced by this statement in the Texas Administrative Code (Title 22, Part 11, Rule 221.13) for Core Standards of Advanced Practice:
e) The advanced practice nurse shall retain professional accountability for advanced practice nursing care.
IF you work as an RN, you retain professional accountability for advanced practice nursing care. In other words, it wouldn't be a valid defense to the board to say: I wasn't working in the capacity of a NP.