Ok, great. A few questions if you don't mind;
Why a Sony tv?
My preference for Sony is mainly due to the CEC implementation. CEC allows devices to be controlled via HDMI. Different manufacturers do it differently. Some will turn on remote devices such as Blu-ray players when the TV is turned on, others will turn on when the external device is powered on. Sony TVs work nicely - OSMC can be fully (?) controlled via the standard television remote. I'm not saying Sony is the only choice, only that I know it's a good one. I rarely have to pick up another remote.
How do you connect the TV with the NAS. WiFi or ethernet cable I guess?
I don't. I'd connect the Vero 4k+ to wired gigabit Ethernet, and the player to the TV via HDMI. I use a grand total of zero smart TV features.
I looked at OSMC Vero but don't quit get why I need it?
OSMC is an excellent platform dedicated to running Kodi, and it does so exceptionally well. Any device, including a smart TV that runs Kodi will do in theory. The Vero 4k+ will play almost any content you download or rip locally, including UHD content. The Vero is not a good choice for you if you want to run other apps however.
Why not the WD NAS? (just curious why you go for Synology)
The WD NAS is more powerful than you need purely for storage. Synology is just a personal preference based on familiarity and ease of use compared to other NAS boxes I've used. They have a range of devices at different price points. If you don't need something capable of transcoding, you can pick something up for a fraction of the cost of the WD unit mentioned.
How important is the internal memory? I do not want buffering. As you can go as low as 256mb which seems to me as really really low?
This seems to be a good option. Agreed? https://www.pbtech.co.nz/product/NASSYN02186/Synology-DiskStation-DS218-2-Bay-NAS-Server-Dual-C
If you're using it for storage, the amount of memory isn't very important. If you're running apps, it may be significant.
I would look at something like this instead...
https://www.pbtech.co.nz/product/NASSYN04180/Synology-DiskStation-DS418j-4-Bay-NAS-Server-RTD12
This leaves room for expansion, even if you don't require redundancy.
I have two Synology NAS boxes, one 8-bay, and an older version of the above. It runs my tvheadend live TV cache for five televisions, records CCTV for four cameras, both via iSCSI, and provides backup storage. Purely for shifting data around, without any transcoding etc., these boxes work very well.
Could you explain maybe what Plex is, when you you say I do not need it. When would you need?
You don't need Plex to view your files from different devices? They all can connect to the NAS?
Correct. If you have a player like Kodi, you can access content directly off the NAS - no transcoding necessary, so long as the player can play it, hence the recommendation for the current best-of-breed Vero 4k+. I can't comment in detail on what Plex offers because I don't use it, but it does allow transcoding so various players can access the content. If you have good players, you don't need to transcode.