I have the same ecommerce business for over 14 years. I went from Yahoo store -> Prestashop -> finally Shopify last month. Since moving to Shopify, I noticed that the site has much higher bounce rate than when it was on Prestashop. The design of the store is virtually the same. The traffic source has not changed. Essentially everything stayed the same except for the platform migration.
Overall, after migrating to Shopify, I see:
One thing unusual is that the bounce rate is especially higher in product pages than say home or collection pages. During the first few days, I even saw bounce rate of over 100% on some product pages. This leads me to think something else is going on with GA scripts and events/pageview triggering issues. But I could be paranoid here.
I am looking to hire an expert that can thoroughly comb thru my home/collection/product pages (not just use GT Metrix) and really look into what could be causing site performance issues. I like to get this solved before going into Q4.
Please reply back or private message me if you are interested.
Can you please share site URL so I can check your site .