Hi ranklein,
If you do an ILS - then you should be in the middle of the VASI / PAPI.
If you do a NPA, then you'll sometimes find you're not in the middle, but well within the tolerance allowed. e.g. Check any LOC only (G/S us) MDA at the Missed Approach Point, then you'll definitely be in the all whites of the PAPI.
A landing from a NPA with the VASI / PAPI all white can be stable and safe - otherwise you'd have to be as accurate when doing a NPA as you are doing a full ILS Approach.
You won't be able to see the PAPI at 1,000 ft IMC.
Some NPAs have MDH below 500ft - so you may be in the whites when you become visual.