For me, more items listed means more views and impressions, but it hasn’t really made much difference to sales.
For around three months after Christmas I experimented with pay-as-you-go rather than the plus account that I’d had for years.
This was for a variety of reasons, but at one point my stock went down to less than 100 items, and I kept it like that for a month or so.
Now, it is back up to around 300.
During that time I noticed no difference at all to sales pattern, but my views were definitely lower.