Here's how I use my Xperia phones and it really useful little tips.
1. Install the fast adb installer and use the command
adb shell settings put global policy_control immersive.full=*
This gets rid of the navigation bar and notification bar to give you all screen. You can. (Still bring them back by swiping from bottom as well dw) also null instead of full brings it back altogether.
2. Now obviously you still need your home back and recents buttons. For this we install. "simple pie" from the play store amazing app. Your buttons can appear by swiping from any place of the screen. Useful for 1 hand usage.
3. Chrome address bar below -
Download Google Chrome beta
enter this in your address bar
Search for "chrome home " and enable it
This helps too on large devices not enough people know about it.
4. Amazon prime and download the amazon video app through the Amazon app and you can watch actual 4k hdr content in 4k hdr. You can also download it offline in 4k hdr and watch it later.
Stunning 4k hdr content obviously YouTube also has stuff but Amazon is where your movies and shows are at.
5. Ds4+ Remote Play
Seemeless connection to your ds4 controller settings/deviceconnection/dualshock 4 and remote play with you ps4 is awesome too.
Moonlight will let you play pc games also if you have a nvidia gpu.
6. Vr testing - Experimental yet but vrtv app on play store played one of my 4k movie I had downloaded and it looked extremely clear although I'm still uncertain only tested a bit because I was afraid off the cheap cardboard vr scratching my brand new device. Still experimenting this...
7. Some Xperia themes are fantastic just look for them on the play store or find free ones that Xperia lounge always seem to give away.
I think for now thats all that I can think of. If any one knows any more drop comment below. My advice is to try the top 3 suggestions I use it all the time it made one hand usage with the x compact godlike. Although with this device it's a little harder though it's still very very usefull.