I will try to answer…
Because the way things are working - the BMS is just broadcasting information on the CAN bus - you can “sniff” alright all the information are exchanged on the bus.
You just need the Arduino CAN module to be configured to the speed of the bus in a passive mode (listening only) and all the frames will be available.
Which frame (ID) contains which information? Just take a look at the topic below and the tables presented there. The tables and all other information are readily available on the web. Just search for Pylontech CAN protocol.
That’s pretty all.