[Tharre]

> But doesn't the ESP32-S3-WROOM have some large on-chip RAM?

They use the same PSRAM chips with relatively bad latency you complained about higher up in the thread. There are boards like those from Pimoroni that even have them on the PCB from the factory.

> For the Pico, say, something in the line of the approach taken by many smartphone SoCs that package memory and processor together.

What for? This only saves you PCB space, the latency is not going to be affected by this. There probably won't be enough people ordering those to justify the additional inventory overhead of (at least) 2 more skews.