The Battery current shunt is mandatory as it is needed to calculate the battery SOC (State of Charge) and gets connected to Battery+ terminal on one side then on the other side to a fuse or circuit breaker and your Load and chargers.
The PV current shunt will be great to have as it will provide way more info as with just the battery current shunt mentioned above all you see is battery current and you have no idea of how much the load uses or how much the PV array is producing.
Example: Say you have a 50A load and 30A coming from your PV array then the battery current shunt will see 20A getting out of the battery and that is only useful to calculate how much energy gets out of the battery and calculate the SOC but you know nothing else.
By adding the PV current shunt now you measure those 30A and so if you add that to 20A getting out of the battery you can calculate the Load and get the 50A load uses thus you know with two current shunts know all the data and SBMS0 can display that for user and calculate the total energy coming from PV, the energy used by the Load and how much the battery was involved in all this so unless you want to save a few $ I highly recommend having both current shunt's installed.
Current shunts are nothing more than a power resistor and they may be spec as a max current they can handle and the voltage drop at that current like say 100A 75mV or as a resistance value and a power rating for the resistor so 0.075V/100A = 0.00075Ohm or 0.7500mOhm (this will be the number you set in the SBMS0) and a power rating 100A x 0.075V = 7.5W
The ADC1n/ADC1p input can read in the -90mV to +90mV range so can read current in both directions while the PVp/PVn current shunt can read current in a single direction 0V to +90mV thus to best take advantage of this range a 75mV current shunt can be used but 50mV current shunts and 100mV current shunts will also work.
You will want to select a current shunt so that your max continues current is no more than 66% of the shunt rating. As an example if you expect a 2000W max continues load from your 24V battery then 2000W/24V = 83.33A and thus a 100A current shunt will get to hot and you will want a 150A or 200A current shunt. You will also not want to jump to a 500A or 1000A current shunt in this example as then your resolution when you measure small current will not be that great.
