Health-wise, some people are allergic or sensitive to sulphites.
Usually the symptoms are a headache (of varying degree) or mild
rash...there are others I'm sure but these are the only ones I know of.

Most people (at least 99% of the population) are not sensitive, and
thus in reasonable concentrations (say 100 ppm or less) it will have no
health effect.

8-12 ppm are produced naturally during fermentation.

For taste/smell, 100 ppm of free sulphur would leave the wine tasting
and smelling of the stuff for most people. Some people can detect
sulphur in very small amounts and thus even 20 ppm will ruin the taste
or smell of the wine for them.

You can pretty much count on every commercial wine that doesn't state
that they are sulphite free or organic having at least 20 ppm to
protect the wine.