My TV has multiple HDMI inputs: most large TVs do. I simply connect the HDMI lead from the Android media box to one of these HDMI inputs, using another input for my Humax PVR.
I connect a cheap optical mouse to one of the USB ports on the Android box. If I need to do a lot of typing, I can swap that for a keyboard.
Mine has an optical spdif output, too, so I can send digital audio streams to an optical DAC, or via HDMI to the TV. Since my TV also has optical spdif output, my digital audio is routed via HDMI, then spdif to my home theatre amp.
It has USB ports that will power a small USB HDD, and, if I rooted the Android, I could run a samba file server, and replace the MyCloud… (Kodi will act as a media server)
It can run the BubbleUPnP Server, which allows me to use the BubbleUPnP media player app remotely.
Being a plain-vanilla Android, it can run whatever media, games, browse, email, social media, catch-up TV, etc apps that are available for it.
For media, I use Kodi, BubbleUPnP or VLC. For PDF, I use adobe reader. Browsing: chrome, Firefox or opera. Email: standard app, yahoo or gmail. As I said, it’s just like a big-screen Android tablet, and will run just about any app you can find on the play store.