My closest equivalent to an NP is a 3rd or 4th year resident. They could be good. They could be very good. The problem is with the lack of depth of clinical training they might encounter a severe case never having seen one before. A good resident will have been through the same. Eager, skilled, smart and will be able to handle tough cases with time but still green.
With residency training, most good programs will put residents in almost every situation imaginable so by the time they graduate they've seen a decent amount. IMHO even good programs won't have trained residents well enough to completely cut the cord. That's why I recommend recent graduates from residency to consider academia at least temporarily, maybe just a few years.
NPs, however, only have weeks of clinical training in a specific area. So say an NP did an office based practice for 4 years. They'll likely know how to do office based work well but if never trained would've likely been locked in a very narrow range of practice. E.g. only a small handful of antidepressants, antipsychotics, mood stabilizers, having hardly dealt with severe patients, not having good clinical experience to know what happens much to their patients while in inpatient or the ER etc.
I would not realistically expect any NP even within the first 5 years of their practice to even have seen 1 case of catatonia and would most definitely based on this not have been able to catch it. Even if they do suspect one, without having ever seen it before they won't have that needed experience to feel confident with what they're doing. Same goes with reading QT intervals in EKGs and correlating it with meds, Tardive Dyskinesia, Charles Bonnet Syndrome, Musical Tinnitus, e (Musical Ear Syndrome) etc.
I had a case where a psych NP made the patient's case of Musical Tinnitus significantly worse. One told the patient that she was psychotic. The other told the patient that her Musical Tinnitus was because a man was secretly implanting the music in her head under the argument, "I don't want her to feel she's psychotic so I decided to validate her psychosis" when in fact Musical Tinnitus IS NOT WHAT WE SEE IN OTHER PSYCHOSIS-if it is psychosis.
If the NP is teamed up with a great attending, is willing to learn and the attending wants to teach that NP I can see being very very very good, even exceeding most physicians but this is extremely rare. As a demographic whole (not individuals) and I've made no efforts to hide this IMHO about half the psychiatrists I see are terrible. This is based on about half of them not having what should be even reasonable IMHO expectations. E.g. I see so many psychiatrists diagnosing patients all with Bipolar Disorder no matter what they have and when asked give indefensible answers such as "that's the diagnosis where no matter what I could argue my way out of it. If they can't sleep I can say they have Bipolar. If they're depressed I can say they have Bipolar. If they're psychotic I can say they have Bipolar." I see some psychiatrists still not knowing the 4-6 week rule with antidepressant trials. (PATHETIC!) But getting to NPs I see about 15% being very good and when I say good it's usually only within the specific area they usually work in.