So- I've touched on a few of these techniques in the past, but this goes more in depth, and a few techniques are significantly more straightforward (and *powerful*!?) My previous method is frankly a tad embarrassing in retrospect (as will be all future previous methods!)
Below's the cheat-sheet for how to set up a "randomized selection from a grid of something". In the Math nodes (currently set to "snap"), you just type in "1/X" (where "X" is however many rows/columns you have on that axis), and it results in the decimal you need- it makes a lot more sense in the video.
Some may be wondering why I used 1D white noise instead of the 4D (which includes an additional "W" slider)- and it's just because as far as I know 1D is pretty darn lightweight computationally, and 4D is many times heavier while giving the same result.

Also- I just put it together as a quick-n-dirty demonstration, but if anyone wants the storefront from the ending of the video to use in anything, here's the blend file! It's got the scrolling sign and a couple other randomizing things in there. 

Sascha Rossier
2022-10-07 15:29:24 +0000 UTCRajarajan Manoharan
2022-08-27 10:29:06 +0000 UTCTheOddGuy ._.
2022-08-05 03:56:25 +0000 UTCRy Ken
2022-02-23 06:55:23 +0000 UTCBrent Holzheimer
2022-01-01 05:09:39 +0000 UTCUrban Exile
2021-12-29 06:00:19 +0000 UTCCarson Reader
2021-12-13 10:04:55 +0000 UTCArsh Waseem
2021-12-02 17:27:53 +0000 UTCIan Hubert
2021-11-26 02:26:51 +0000 UTCFrank Frohnhoefer
2021-11-21 19:25:36 +0000 UTCNicholas Cummins
2021-11-21 00:30:12 +0000 UTCPablo Nicolas
2021-11-19 02:56:22 +0000 UTCash katchum
2021-11-18 17:04:07 +0000 UTCShawn Hawkinson
2021-11-18 08:19:30 +0000 UTCPete Burges
2021-11-17 00:08:55 +0000 UTCArmando Marchetti
2021-11-16 22:56:22 +0000 UTCTolga Katas
2021-11-16 22:50:51 +0000 UTCLonnon Foster
2021-11-16 18:31:56 +0000 UTCGabrial Wolf
2021-11-16 18:13:25 +0000 UTCDannysh Rosli
2021-11-16 15:14:28 +0000 UTCPaul McBryde
2021-11-16 13:30:50 +0000 UTCJostein Lie Svalheim
2021-11-16 09:36:15 +0000 UTCZeke Faust
2021-11-16 09:32:14 +0000 UTCMahdi Poursamad
2021-11-16 09:17:19 +0000 UTCJostein Lie Svalheim
2021-11-16 08:57:13 +0000 UTCDawson Henderson
2021-11-16 08:48:42 +0000 UTC