Frank Goossens on "[Plugin: Autoptimize] Can I use it with other cache plugins like "WP Fastest Cache"?"

in general it is even advised to use a page caching plugin to accompany AO.

Specifically for WPFC (and W3 Total Cache) one should however take care not to use the built-in minification (CSS/JS/HTML) but to let AO handle that.

hope this helps,
frank