1000s of LEDs - arranged how? Actual multiplexing?
Say you had 32 x 32 array, 1024 LEDs.
Approach is the same - use cd74AC164 to source current to anodes,
or 74HC595 with MIC2981 as current drive buffer,
and
74HC595 driving N-channel MOSFETs to sink current from cathodes.
Wiring up tons of individual components is tedious and prone to errors with all the repetition.