@ Cheap, it's a huge topic on its own... There'll be a minor update shortly, to address some minor CLS issues
. The demo is hosted on a fairly low spec VPS to be honest.
Unchecking "Enable buttons "Buy Now" and "Add to wish list
" in the products list" in General Settings > Appearance will reduce the DOM size somewhat on the homepage and catalog pages.
You can 'trim' down the template somewhat (CSS & JS) to make small extra gains, but you'll probably need a reasonably experienced developer on your side to make the changes.
If you look at the trends in other ecommerce platforms, eg. Shopify; stores tend to be going more lightweight in content/presentation, in order to get better scores. It's possible to make changes via the reBOOT settings to do the same.
You can search back through this thread, as it's been talked about/addressed before, but in the meantime, you can check the SEO tips
Having had the unenviable task of working with Woocommerce over the past couple months (don't ask), I can tell you that in terms of SEO, X-Cart Classic and reBOOT beats it hands down
I might write a longer article dedicated to SEO in general, as there's so many factors involved, ie. not just the template itself.