No offense, but that entire approach is just… pointless.
Is it?
Let's say you construct 11×11 matrix using WorldSemi WS2812B-V5/W 5050 RGB LEDs on one-sided aluminium 88mm × 88mm boards (8mm or 0.315" center-to-center spacing), using JLCPCB; for a total of seven units, or 55×11 display; total 440mm × 88mm or 17.3" × 3.4". The 605 LEDs cost $46.10, and manufacturing and assembling the boards somewhere around $20 or so. There is room for 0603 supply bypass capacitors, too. With shipping, let's round up to a full $100, although $80 is probably closer to the reality. Maximum current draw of each panel is 4.4A.
JLCPCB has IS31FL3729-QFLS4-TR (C2940549) 15×9 I²C LED matrix controllers for assembly at $0.74 apiece. It has one address setting pin, which can choose between four different slave addresses, so at most four such modules can be used in one I²C bus. It does work up to 1 MHz, though.
Let's assume you use Honglitronic HL-AM-2835H421W-S1-08-HR5(R9) 4000K SMD2835 LEDs (C516127) with a 3.2V forward voltage, run at less than maximum current, say 20mA each. The
datasheet indicates the relative intensity scales about linearly, so the luminous flux should be about 7.5lm. At 5mm×5mm matrix, each 15×9 matrix would be 75mm×45mm, so say 75mm×75mm for each panel.
Let's say you make ten such panels, for a total of 750mm × 45mm display area, 150×9 LED matrix.
The 1350 LEDs would cost $18 at JLCPCB assembly, the ten controller chips $6.60, the smattering of capacitors and resistors say $5, and manufacturing and assembling the boards (one-sided aluminium if possible wrt. routing!) about $20 or so. Say $80 or less shipped.
I do believe this would be well suited to run from a 4V, supply; to drive all ten, you either need three I²C buses or use an I²C multiplexer.
Each of the modules should be able to produce a thousand lumens of luminous flux (at 20mA per LED, 2.7A per panel, 11W if run at 4V), so heat produced will limit the actual brightness in practice. These LEDs also have 120 degree spread, so they're not the best for this purpose, but I was thinking of some kind of a diffuser with inter-LED barriers here.
Thus, I can definitely see a point for creating ones own matrices. I do not think it is the best choice in this case, but it is a valid one, depending on the needs.