Files browsing app

What is the best software application that cleverly uses real estate, is "complete" / featureful and works well on Onyx devices? It's a dire waste to have a device as big as office paper and display only a handful of information.

The shipped filesystem browser, "Storage", is also missing critical features: as just noted in a parallel thread, the "share" icon is omitted (pretty severe forgetfulness in a device that already is missing several important communication functions - OTG, SD-Card).

I noticed only earlier that Android 6 has a filesystem browser in the Settings, Internal Storage > Explore.