If you want to use 10Gbps in your home you will need computers with 10Gbps cards which cost $200 each or a $600 motherboard with 10Gbps connection. A 10Gbps switch which is crazy expensive over $700. Then you need very good Cat6 cabling for short distances or Cat6A for longer distances. It just isn't feasable at this point in time for home use.
Next you have to consider what you will use to stream movies to your TV. A PS4 or XBox or smart TV is only 1000Mbps. A Roku is the same. An Android box is the same.
Here are my tips for getting full use out of a NAS. Keep in mind my experience is with Synology NAS' which I have had great experiences with over the past 10+ years and highly recommend. I do not have experience with other brands.
1. In my experience with a NAS, 1000Mbps connections is enough to stream 4k movies.
2. Gigabit ethernet is 1000Mbps or 125MB/sec. 1000 Megabits per second is actually 1000/8 or 125 Megabytes/sec. Do not assume just because your computer, router, switch, cables and NAS are all gigabit that you will transfer at 125MB/sec in windows. You may be surprised to only get 10MB/sec or even less. The speed a NAS transfers at is related to it's CPU and RAM and overall hardware power.
3. Synology advertises the upload and download transfer speeds of each of it's NAS'. The more expensive and powerful ones are faster.
4. Let's say you are downloading a 15Gb HD movie. Do not download it to your computers hard drive. Instead set your software to download the movie directly to the NAS. That saves you the hassle of having to transfer the movie from your PC to the NAS afterwards which can take over 30 minutes.
5. If you want to move files between locations on the NAS do not use windows to copy or move and paste on the NAS. This can take a long time as it has to move the file to your PC then back to the NAS in the proper location. Instead use the NAS' built in GUI interface software and move the files that way instead of using windows explorer.
So to conclude gigabit is enough for a home network running 4k movies of 20GB+. Make sure your streaming devices (Roku, android box, smart TV, etc....) are all gigabit and not just 100MB/sec. Check the upload/download speeds advertised for the NAS' and consider spending a bit more for a more powerful version that is faster. And finally learn your NAS inside out and use it properly. For example Synology's software is called diskstation so you need to learn to use that. One last thing I can recommend is to get a 2 or 4 hard drive NAS and set up a mirrored RAID so that if one drive crashes you don't loose your info. Then get 2 NAS rated hard drives such as western digital REDs. They are designed for high traffic NAS specific workloads and are more reliable and last longer. 2 x 6TB drives in a mirrored RAID would give you 6TB of space which is pretty good for a movie/music server.
In my particular household I have 2 PCs each with a 256GB SSD only. I do not need storage drives in the computers since they both use the NAS. The money saved on hard drives in the computers is used to buy hard drives for the NAS. Cell phones, tablets, XBox, Android media players, Grace digital alarm clocks all access the NAS. My alarm clock wakes me up by streaming music off the NAS. My computers can all be turned off and the MyGica Android boxes can stream movies off the NAS in the living room. I wouldn't have it any other way. I personally own an 8 year old Synology with 2 Western Digital Reds. It's still rock solid so I'm confident in the reliability of both. The only downfall is the performance of my NAS but it's 8 years old so that's a given. My next purchase will be another Synology but a more powerful one with more RAM and a better CPU to increase speeds. I never wish I had 10Gigabit speeds since I cannot even max out 1 Gigabit yet I can stream 4k no problem.