Some of these issues seem like Shopify issues rather than my specific store. After looking at page speed insights for a few Shopify stores, I haven't seen any with perfect scores. Any idea on how to fix, or is it impossible?
It is possible to increase the score but I had not seen 100. And this is because there are some assets injected by Shopify and 3rd party APPs that you do not have access to.
The overall score is not really the goal but having a low initial render time.
I usually use https://www.webpagetest.org.
You can set up various performance test that are performed on selected 3rd party servers.
Here is a load test: https://www.webpagetest.org/video/compare.php?tests=160809_D2_RPB-r:1-c:0
The test is performed on California USA - EC2 - Chrome - 3GFast
On the waterfall you will see what is loaded and the time that takes.
Yes it is possible - we have Collection pages with 40 products, colour swatches, overlay images scoring 90. CMS pages scoring 91 to 95 and homepage with a good level of content scoring in the 85 / 89.
Takes a lot of code work and any apps will effect performance metrics so split and test so you know the hit every single app has on your site.
Test on lighthouse and google page speed and pay close attention to the weighting ( CTBT (Total Blocking Time) is 30% and LCP (Largest Contentful Paint) 35% so improvements to these areas will give the biggest impact with the least work. Some tips below: