Your friend is an idiot. You’re right you can plug in 3-5 displays that are all the same resolution and span the desktop and games across all of them as though it was one large display. This feature is called NVIDIA Surround. That’s what you should be searching for videos on.
You just should be able to plug all the displays in and go into the NVIDIA control panel and enable the Surround option. This will launch a wizard that walks you through setting up your Surround configuration. When it’s done, you should have the desktop spanning all 3 displays as though they were one mega display, and games will see the displays this way too and offer you the corresponding wider resolutions in their graphics options.
Not all games will give a good experience in NV Surround and AMD Eyefinity (on NV and AMD both). This is because many games intentionally prevent the FoV (field of view) from being widened to fill in the side monitors because extra visibility that only some poeple have would be a sort of cheat (unfair advantage). In these cases the view will either be zoomed in or stretched horizontally, both of which are unplayable and defeat the purpose. You can see examples of this here:
Also some games seeing the displays as single large and wide monitor means they end up sticking your UI (minimap, health, etc.) on the outer corners of the outer displays... meaning you can’t see them as easily at a glance as if they were properly limited to the center display. Games that properly support and take Surround into account limit the UI to the center display.
To the game, the NV Surround and AMD Eyefinity look identical... just a larger mega monitor.
Also, NVIDIA’s solution is similarly easy to AMD’s. They’re almost identical. Though AMDs may be a bit more flexible on what varied combination of displays you can use in such a configuration... at least it used to be so.