Yea NU7100 is the basic 4K TV of Samsung for 2018.

As for the other options you have several choices.

The NU7400 is like NU7100 but comes with an extra feature called Wide Color Gamut , which can show more Vivid colors when playing HDR content. If you don't watch HDR content this feature is useless for you.

The MU6300 is a 2017 Samsung Basic 4k Model , it is pretty much like NU7100 but slightly brighter , has better remote controls / voice control . It has been discontinued but you may still find some merchant selling it .
Since this is a Samsung thread , I really shouldn't recommend models from other brands here

Yep , I know it sounds silly .
Beside the steam link feature & slightly lower input lag , NU7100 isn't actually better than MU6100 / MU6300 .

There is also something to be noted , the NU7100 does not supports WIFI 5 GHZ ,  the MU6100/6300 does.

It is a basically a device that connects your TV with the Steam client ( a game platform ) on PC , so you can display PC games on the TV screen.

Theoretically for WIFI streaming , it can allow speed up to 1Gbps ++ . But the CPU of the TV (which is kind of weak ) also play a part in processing the data , 100 ~ 400 mb/sec is a more realistic expectation.
Base on many of the TV models I have inspected ,  none of the current TVs ( except a certain China brands such as TCL ) has a gigabit Ethernet port.
Including the high end QLEDs and OLEDs.  It is pretty safe to assume most of them has a 10/100 , 60 mb / sec is pretty much the reasonable expectation.
For modern day Apps streaming , that should be sufficient. Primary because streaming videos suffer a major loss of video quality ( bitrates ) in the process of transcoding . 
For eg , the 4k movie on Netflix is of much smaller size than its 4k bluray counterpart . In reality , the so called " 4k " streaming video quality is more or less the same as what you see from a 1080p bluray disc , which is quite a bit of downgrade .
If you want to stream very high quality video files such as 4k Bluray Rips and remux from your HTPC / NAS , the Ethernet LAN port is unable to handle the massive data transfer . You have to rely on WIFI streaming but this can be problematic due to many of the 2018 basic 4k TVs do not support 5GHz WIFI.

Your alternative , is to connect the TV to an external storage via USB which can be very hassling .

It really depends on the quality of the files and how it is ripped.

For the pristine source of Ultra HD Bluray quality , there will be some buffering and stuttering around.
You are better off with a media player .