.... Attached image with a fuse for each battery added ... the max current is >20A ....
Yup, your choice on type. I'd say use a ~30A fuse. If 1 battery in the chain is supplying more than its share, somethings up. Like Psi says,
they should self equalize, and have no reason to drift too far apart.
.... "Active Balancing embedded control electronics with Microprocessor control"
Yeah, active balancing WITHIN each battery pack, stand alone. Each pack has NO idea what the other packs are doing. PLUS, I have
rarely found the
embedded BMSs to be true active. Usually they
only SHUNT excess voltage to try to match up all cells. So, if only 1 cell goes low, they shunt ALL the others
to match it. Adding voltage is a much more complicated task - using bi-directional DC/DC converters. Done a few, it requires a LOT more bulky electronics.