Hello!
In my opinion, shops with not as many items are more likely to get more sales. People do like a variety, but they also love stuff that you can't find in most shops.
You're more likely to have two of almost the same thing with more listings, (which isn't bad at all) than to have something different and unique with fewer. Another thing is that if you have tons of listings you tend to think up the same idea for a listing (which, again, is not bad at all) whereas if you have fewer listings you get more creative.
Your shop is very nice, too! I think you should be okay with less than 30 listings, in my opinion. Don't take my word for this, because I'm not 100% sure, but I hope this helps! :)
Eden