Author here: thank you for this deep dive. I saw peaks of 5.9 Mbps, it might be possible to increase throughput by allocating more memory. The link between the rp2040 and Infineon Wi-Fi device is 31.5 Mb/s. It might be possible to push that out over PIO to an external USB 2.0 PHY. Apparently the Wi-Fi device is capable of higher speeds. Who knows what will be the limiting factor. I'll leave it to someone else to experiment, my focus was the stock hardware without any modifications.