Great tip with #1. For #2 rather than removing apps, I would start with removing old app code first. We often find leftover code from apps that have been deleted but not removed from the theme code (many apps add code to the theme, and access is restricted once you delete the app so it cannot cleanup after itself).
#3 (using AMP) will depend on the store design, AMP is great for simple layouts but if you have complex layouts + features, it could actually hurt your conversion rate. The way I like to test this is by creating an AMP page(s) and run paid traffic to the AMP page and the non-AMP page. If conversions are the same or better with AMP, then AMP is definitely the way to go because of the speed increase.
These are just a couple tips, but to see what specifically can be optimized for your store the Shopify Analyzer will reveal optimization issues. It’s a tool my team of Shopify optimization experts built free for the community, the scoring is based off over a thousand Shopify sites we’ve optimized.
Both store owners and agencies use it regularly to optimize Shopify sites specifically without the poor recommendations general tools can sometimes give that can damage ecommerce sites.