...cannot find any other page speed performance apps for things such as minfy js/css/html etc do any exist?
Shopify apps work differently to wordpress so I wouldn't expect such tools to exist. You've got control over the assets in your theme so you can minify the css and js. For css ideally you'd want to be using scss.liquid files since it minifies automatically.
HTML minification can be acheived as well but gets a little riskier. Your theme has to be ready for this. I've minified parts of mine (here) so you could look at the source to see what can be acheived.
Many themes in the store could do a better job of squeezing more performance IMO. They are decent, but there's improvements that can be made. Themes found off shopify (like on theme forest) are generally worse for performance.
Image however you're kind of stuck on. It would be nice to see image compression / controlled improved in the future.
Specifically on your home page:
- Your site is loading 458 things on the home page
- 20 css files. That's way too many.
- 39 js files. Some could be app scripts, but again this number should be way less.
- 195 images. Most of those probably don't need to be loaded right away, but rather on demand.
Those are not Shopify specific issues, but rather how the theme is built.