After some trial and error and searching of forums here are some solutions to common problems and questions of users of N950.
1) LACK OF BASS, BASS FROM SUBWOOFER IS VERY SUBTLE - SOLUTION
The overal bass volume from subwoofer and its quality is VERY dependent on the subwoofer placement in your room.You need to check different locations in your room for subwoofer placement. There is a general "golden rule" of subwoofer placement - corner of the room. I found the sweet spot for the placement in front left corner room between wall and the cabinet (of course for you it may be completely different place). After checking four different locations in my room, I found out that the bass is louder when the speaker of the subwoofer (side with the cloth on it) faces anobstacle (cabinet). When subwoofer was facing open area of the room the bass was very subtle. So the subwoofer is not weak , with proper placement it can sound very loud and deep for every sound source, not just for ATMOS sources.
2) PROBLEMS WITH CONNECTION TO SMARTTHINGS APP - SOLUTION
Finally, I have managed to connect to Smartthing app after several fails. Here is what I have done:
1) I have powered down my wifi router and N950.
2) Powered on my Wifi Router back, waited for wifi network function to be operational
3) Powered on N950. I checked if every speaker was connected.
4) I switched the source to WIFI on N950. Display of N950 showed WIFI NEED TO CONNECT
5) I pressed and held the Network button on the bottom of the N950 for couple of seconds - display showed WIFI NETWORK
6) I runned the Smartthing app, the N950 was seen by the app, so I tapped to add it.
7) After couple of seconds dialog appeared with my wifi network name and password to be added.
8) Filled my Wifi password and the app finally added N950 as a device.
3) EQUALIZER WITHOUT ACCESSING OF THE SMARTTHING APP - SOLUTION
Just hold OPTIONS button (gears) on your remote controller for more than 5 seconds. Then press left / right to access frequencies and up / down to boost or cut. If nothing happens, try to press and hold the button once again. I really recommend to play with EQ as it improves the overall quality of sound. With proper subwoofer placement you will get deep bass so you will maybe need to enhance highs and cut little bit mids. My preference is is to cut 1.2KHz by -1 and then bost 2.5KHZ by +1, 5HZ +2 and 10KHz +3.
4) CALIBRATION, LEVELS - basic SOLUTION for 7.1 (not for 7.1.4)
This can not be done just by the soundbar itself.You need to have microphone and SPL meter. For very simple solution you can download SPL meter app for your mobile, and then either use phone microphone (less precise) or connect your phone to an external microphone. For sound reference level I usedDTS HD Master Audio Sound Check 7.1 video:
Copy the file on USB and play it either via XBOX ONE S/ X (I used VLC app for XBOX ONE) or PS4, or any device capable of decoding the video and 7.1 audio. Set your audio output to Bitstream out - dolby ATMOS, or uncompressed 7.1.
Put your phone or microphone to your listening position. Adjust the overall volume level to 13 or more depending on your room size. Be quiet, close your windows, turn off everything which produces sound (send your wife shopping, and kids outside :-) )
Then you have to write downaveragelevel of every speaker level when playing white noise sound from the video (follow video instructions and write down average levels shown in SPL meter app). Do not bother with subwoofer level, it is hard to do calibration of the subwoofer this way.
You may need to repeat the measurement process several times (4-5 is enough to minimise errors) and then make an average of your all measurements for every speaker (excluding subwoofer)
I have got these results (this is valid for my room with dimensions of 3mx5m and my rear speaker placement on back sides of my couch, very slightly behind of my listening position on both sides):
CENTER speaker is +1dB louder than FRONT LEFT and RIGHT. Surround speakers are louder +2dB than FRONT LEFT and RIGHT. The SIDE speakers are very loud, almost +7dB then FRONT LEFT / RIGHT (probably for sound to be able to bounce from walls/obstacles).
So if you want to sound channels to sound approx. equally then you need to cut those speaker levels by measured difference vs. FRONT LEFT and RIGHT. (in my case to cut CENTER by -1dB, REARS by -2dB,...)
However, by cutting SIDE speakers by -6dB (this is max you can do in N950), the surround feel of side speakers is less hearable, so its your choice how to cut the level. I decided to cut them only by -2dB).
This is only very simple approach of calibration and only for 7.1. You can not measure the four upward firing speakers this way, as the test video is only for 7.1. If someone has 7.1.4 audio test with white noise samples, please post a link.
For info, my N950 is running FW 1001.2 as a factory default. I decided not to update to 1001.3 as some users have problems after the update. You can switch off auto update feature in Smartthing app on main screen.
Just to add to 2 above: I wasn't able to connect the soundbar to wifi when using the SmartThings app. I tried all the suggestions in the various forum posts I came across and still wasn't able to connect. By accident, I managed to get the soundbar connected to wifi. It turns out the SmartThings app running on Android 8.1 did the trick. Initially I was trying with the SmartThings app running on Android 9. So if you are running into this issue and using a device with Android 9, try using a different device with a lower Android version. Once you are able to add the soundbar to the SmartThings app you can go back to using the SmartThings app on Android 9.