what are the pros and cons of using fiction, drama and essays to study
medical history and what do these sources convey that more fact-bases
sources cannot?

I recollect that A J Cronin was a GP

It seems fairly obvious that people who know about their subject, and
wrote about it while it was current, are a pretty good primary source.

Of secondary value would be people who did not really know the
subject, but wrote about it anyway.

The least reliable stuff is 'reconstruction' - where somebody reinvents the past.

The trouble with 'official facts' is that they are often sparse, very
often misleading. For example I know of two people who died of cancer,
yet the autopsy report was 'liver failure'.

In essence, you are asking what is the difference between Qualitative
and Quantitative research.

I sincerely hope that you discard 'reconstruction', unless you can
find its contemporary sources.