Hello Mark2021, this TV uses our SmartCast Platform which offers a host of built in apps, as well as support for Google's Chromecast, Apple's AirPlay 2, and voice support for SIRI, Google Home, and Alexa. You are not able to manually download additional apps, however new apps are added to the platform often. If you find there is an app you want to watch that is not on SmartCast you may be able to cast it using Chromecast or Apple AirPlay from your phone or mobile device. In regards to audio, as televisions continue to have larger screens with thinner profiles and sleeker bezels, there is less room for large speakers. To help get the best audio quality out of your VIZIO televisions speakers, we’ve included settings like DTS Studio Sound to provide the highest performance possible, while maintaining the thin, sleek, bezel-less profile of your television. If you’d like any help adjusting your audio settings feel free to contact VIZIO support at 844-254-8087. For top of the line audio performance, you may also look into purchasing a VIZIO Sound Bar, there are several models available with wireless subwoofers for enhanced bass, rear speakers for true surround sound, and our new line of Atmos Sound Bars.