Yes, the board 3.0 is a different beast with some changes in the schematics. The main differences respect to the board v.2.0 are:
The power on / off state of the Pi is controlled by an ATMega328P MCU (or an Arduino nano as an alternative) instead of a latch circuit made with capacitors and resistors. So the board v.3.0 is compatible with the Pi 4 and it is future proof (see here to know more about the problem of the board v.2.0 and the Pi 4).
The external buck and boost converters module have been replaced with two on-board circuits made with common components (inductors, mosfet, diodes). The output voltage is controlled by the same ATmega328P MCU (or Arduino nano) that controls the Pi power status and it is regulated via software in the firmware.
Since the Pi 4 has more serial ports available on its GPIO, the second MySensors gateway (NRF24) now runs on a dedicated ATMega328P MCU (or on an 3.3V 8 Mhz Arduino Pro Mini as alternative) located in the right part of the board.
The on / off status of the FAN is controlled by a GPIO of the Pi and can be automated in Home Assistant on the basis of the CPU temp. This makes the hub more silent.
A connector for a separated set of IR leds (suitable for the night vision for a camera) controlled by a GPIO pin has been added.
I have ordered the board 3.0 last week, so hopefully I should receive the pcbs this week for testing. After that and an update of the d-diot image I should be able to make it available in the PCBWay bazaar
Let me say that, due to the use of the additional serial ports that are an exclusive of the Pi 4, the board v.3.0 is not fully compatible with the Raspberry Pi 3.
You can use it with a Pi 3, but without the second MySensors gateway (NRF24) and the 433 Mhz gateway (RFLink); on the hardware side this means that you don’t need all the components that are on the right side of the vertical white line in the picture above.
In any case I have some unused copies of the board v.2.0 that are simply collecting dust, so I can send to you one pcb. If you are interested send me a private message.