Flashing
Tests show that esptool flashing speed saturates above 1152000 baud. Is this due to a hard rate limit imposed by the driver or protocol layer to keep communication stable?
This happens because host-side and chip-side processing time has already become the main bottleneck. Simply increasing the baud rate no longer provides a meaningful improvement in download speed.
esptool itself does not enforce such a limit. Under the current conditions, there is no practical way to further increase flashing speed.