As you can read in that article, the guys from Front Pictures used a single machine with just 2 Nvidia Quadro cards (each Quadro has 4 outputs) to scale to 64 unique outputs using several additional display wall controllers (such as Datapath x4).
You can scale this either:
vertically (add more Nvidia quadros to the same machine, limited by motherboard)
or scale horizontally (divide the load over multiple machines and sync their playback).
Depending on realtime rendering demands and budget you could choose:
the most powerful option with 18 Quadro cards (which will give 70 outputs + 2 for UI). This would be good if you have lots of realtime rendered interactive content. 18 cards obviously will not fit in a single machine
less Quadro cards and split their output signals with more display Wall controllers until you have 70 outputs + UI screens. (for instance if you are just playing back pre-rendered content and don’t need that many GPU cores)
To give an example here’s an example of scaling horizontally with the most powerful option, were I designed a cluster of 4 machines, each with 2 Quadro cards with 4 outputs, running 8 instances of TouchDesigner in sync: (see bottom photo for setup)
Send me a message if you need someone to spec your hardware/software architecture.