So the answer is yes, Of course you can optimize other things that are not related to AMP - such as the content of the page can still be crafted for search engines.
Here is our trick as promised to determine if your website is mobile first search optimizated. This is just a test you can do today that is current for early 2018.
Voice Search SEO is simple. If are a client of mine your websites are already voice search optimized - if you blogged.