OctoWS2811 VS WLED

I highly recommend the Teensy 4.x with the OctoWS2811 driver. This driver provides 8 channels of parallel output using DMA data transfers to offload the CPU. I think that meets your criterion for "hardware SPI". It doesn't seem like the T4 is overkill for what you're doing, especially if you're using floating point math. The T4 is blazing fast, and I've heard mixed reviews of ESP32 FP performance.

They are actually quite easy if you have some cash. Check out NeoPixel at Adafruit, they have a detailed guide on how you can control strip lights. NeoPixels are great but a tad expensive, you can find less expensive strips on discount resellers, search for “RGB Addressable LED Strip”. Some offer a control module but you will be limited the the built-in color patterns and speeds. If you can solder and program an Arduino you can modify example scripts to do a lot of things, even create digital signage and video walls.

Assuming you're going to use the OctoWS2811 library to drive the LEDs, the maximum possible frame rate for 2 channels of 1,008 LEDs should be:

However, if you have all 600 LEDs in a single strip, and the strip is WS2812, then you're limited by the internal refresh rate of the LEDs, which brings you to about 55hz. Which is ok, but if you spend much time in-between refreshs, maybe it's not fast enough. Certainly not for persistence-of-vision. If you're happy to break your strip into several sub-strips that get their own data line, you can speed up the refresh rate a lot. If you're using a Teensy 4, you can use this library for example, which allows you to efficiently drive many LED strips at once: https://www.pjrc.com/teensy/td_libs_OctoWS2811.html

You can also check out OctoWS2811 https://www.pjrc.com/teensy/td_libs_OctoWS2811.html

I've used RGBW for a number of projects involving non-addressable LED strips and spot lights. I haven't yet needed RGBW for a project requiring addressable strips, but it's in my tech roadmap. I no longer use FastLED, and I've written my own HSV/HSI-to-RGB/RGBW color conversion library. I use the OctoWS2811 library (not the adapter board) for DMA-based serial data output to addressable LED strips. It appears that this library supports RGBW strips, but I haven't tried it yet (others are doing the same). See the last few paragraphs of this article for more details.

But the OctoWS2811 Library can only use 8 Pins, at least on the page is only for a Teensy 4.0 and 4.1 the hint, that any group of pins is possible.

For line in, is the ADC really not that good on an ESP32? Or is the signal conditioning circuit shown on this page workable to get a reasonable output? https://github.com/atuline/WLED/wiki/Analog-Audio-Input-Options I notice that there is circuit diagram on the page for switchable analogue mic or line in on this page - but from what I've read the digital microphones are much better options.

Je me trompe avec le son réactif Sound: [https://github.com/atuline/wled/releases/tag/0.10.1 )

Refer to this https://github.com/atuline/WLED/wiki/Analog-Audio-Input-Options