I'm working on designing a video wall with 12 monitors in a 4x3 grid

Not sure where best to start this question since I’ve been working on this for a few months now and the threads I’ve read here go over my head quite a bit.
The wall is going to consist of 65" monitors, 1920 x 1080 to start but may advance to using 4K resolution later.
Datapath is a company that creates hardware and can take a single input and output it to 4 monitors. So I was looking at getting three of these and using a NVidia card with 3 outputs that can be sure to sync themselves.
I just learned about Mosaic today so I’m not sure if that’s a better way to go and find someone to build a computer that can handle 4 NVidia cards (12 monitors for the wall and one for the desktop is 13 monitors total thus 4 cards instead of 3). My research is telling me to use RTX A6000 cards. However I don’t see those in the products page. Any advice would be greatly appreciated.

Just saw some info on the NVidia NVS 810. Which is tempting but may not be good to handle the production software I’ll be using “Resolume”. For the most part the video wall will just be playing a looping 1920x1080 mp4 file but the salespeople want to be able to click a button to pull up a different requested demo video on the fly, hence the need for production software.