Jason here from Shopify Support.
What a beautiful store! Your design aesthetic reflects well with your brand and the products you carry. You're also asking great questions. I admire the fact that you've done thorough market research. Skincare is competitive and like most of the cosmetic products, can be deeply personal. Your insightful question shows you will be able to grow with your brand. Here're my suggestions on how you can improve your store's user experience. Also, my take on your assortment question.
Overall, you have a great store with a solid foundation. These are the tweaks that can help you convert the visitors into shoppers. Because there's quite a bit of information here to go through, I've left some open-ended for you to think them over. The goal here is to trigger you to think again on how you want to position yourself in a competitive market and how to use a different design strategy to help you increase the conversion.
Now we've covered the design/layout of your store. How're your marketing strategies going? What have you tried to drive traffic to your store? I can see that you're growing followers on Instagram. If you haven't done so, I encourage you to check out Shopify Academy. It offers great free tutorials on various digital marketing strategies, including the often overlooked email marketing.
If you want more pointers on any specific suggestions, feel free to reach out here. I'd love to discuss it further.
All the best,