First, enable the Developer option by pressing the Build Number multiple times, which is present in your Settings>About Phone. Enable OEM Unlock, also Enable USB debugging option by pressing Menu>Settings>Applications. Download ODIN file, auto-root kernel file and the Samsung USB drivers. Unzip the ODIN zip file and install the exe file. Find and select 'AP' hit start after that. When you see 'Pass' reboot your phone. Install and run SuperSU, you should have full root.
Yes, the Galaxy Note 5 supports Google cardboard. When I bought the Google cardboard I didn't know how to use it. But I saw a video of how to use google cardboard, it helped me a lot. Turns out that all you have to do is to install Google cardboard app first.
The Samsung Galaxy Note 5 is available in Sapphire Black and Silver Titanium colour. When I went to the store, both the colour looked equally good. However, I went for the Sapphire Black edition as it looked quite cool.
Just like most of the Android phones, the Note 5 also tends to heat up when I play games or use 3G/4G data, the metal body often acts as the catalyst. But in case the heating issue rises to un uncomfortable label, just keep the phone in standby mode for a few minutes, it will cool down soon.
Just like the other Samsung headphones, the Samsung Galaxy Note 5 has good headset. But if you want better sound effect, you should buy a good quality headset. I bought an additional Sony headset for its bass depth audio enhancement.