Yes, that should give you the RCORE carrier board plus the Wi-Fi/BT Carrier Board. You can then put your existing RK3588 into the new RCORE carrier board. The Wi-Fi/BT Carrier Board comes with the Intel AX210 Wi-Fi/Bluetooth module for Wi-Fi 6E and BT 5.3 connectivity which give you bluetooth.
I don’t know. Maybe they are compatible.
The firefly RK3588 board sits very tightly on the RCORE carrier board. I don’t think it’s compilicated but it needs careful prying of the RK3588 from ith carrier board by slowly lifting each corner by a fraction of a millimeter until it comes off.
If you still have the old backplate you definitely want the new one or otherwise the wifi signal reception will be very bad.