Shopify page speed is most affected by the codes in the theme, apps and the images used. To improve the codes, we will have to minify the files, strip away the unwanted excess codes like CSS and js, combine the different code files together and optimize the codebase. To optimize the app we can code the custom function right in the theme template or choose alternative apps that don't affect the speed. To improve the images, we will have to reduce the image resolution to optimal size, compress images, opting for the right format.
I am a Shopify expert solely working on Shopify stores for more than 6 years and I have extensive knowledge in LIQUID code that Shopify stores are built with and HTML, CSS, javascript, and API, hence I can increase the page speed without affecting the existing design and the functions. I have worked with the many famous themes and know my way around the theme code.
You shall check the recent reviews left by my clients for my page speed optimisation projects as reference.