The load is the power you use. Have you done an energy audit to see how much power you use daily? Or how much power you use at any moment?
If you are planning on getting an inverter (to run AC appliances for example), do you know how big it will be?
Lets say you're getting a 3000w inverter. When used at capacity (3000w, like 2 hair driers at the same time)
will be:
3000W / 25.6V = 117A
In this case, a 120A BMS would be sufficient. A cheap BMS would likely need to be "rated" at 200A to work in the real world. A quality BMS like Overkill/JBD, Battrium, ... would work as specified in my opinion.
Similarly, if you had a 200A battery charger, your BMS would need to handle this but its more likely your inverter load will be higher than your charging amps. The BMS monitors the maximum current flows in and out of your battery. When this current is exceeded, it cuts off and "protects" your battery.
Make sense?