bad ttfb with autoptimize

1s extra TTFB is not normal no, this probably means the cached files cannot be reused and your cache will grow quickly. try re-configuring AO to ensure maximum cache reuse (see AO FAQ on how to cache size under control)

additionally I do advice people to have page caching (e.g. wp super cache/ key cdn cache enabler/ …) to ensure TTFB is kept to a minimum.

hope this helps,
frank

Good progress there Tim. Regarding the mobile pagespeed score; ensure the CSS is not render-blocking should result in better first paint times and thus also a better pagespeed score. To do so have a look at the “inline & defer CSS”-option in AO, see the AO FAQ for more info.