We've started tracking Shopify speed tool scores on about the last couple hundred sites we've optimized (speedboostr.com), the range we see is usually between 20 - 35 for active stores using apps, with the average being 23.
Optimization usually raises the score a little bit, but the score with that tool is largely based on the 3rd party apps you use so it's common to score low if you have store facing apps. It uses Google Lighthouse, the same general engine that Google PSI uses. To see how apps affect the score with that tool we did a case study: https://speedboostr.com/how-apps-affect-load-speed.
A 40 is a pretty good score with the Shopify speed tool if you have an engaging site.
Founder of
Speed Boostr (Shopify optimization experts, theme customization, custom app development).
Creator of
Shopify Analyzer (first performance analysis tool for Shopify sites, free for the Shopify community).
Creator of
Order Automator (auto tag orders and customers + auto fulfill orders + email notifications).
Creator of
Theme Scientist (A/B testing app) and
Tip Jar (add a tip button to your store).
