Hi, I have abandoned the idea of buying ready-made batteries because the advice of some experts highlight that it is highly discouraged because they have two separate bms and therefore they can go into imbalance and create problems. What you write about a balancer personally is an excellent choice, because the balancer 8 that is good and reliable and branded), manages to balance the batteries. I have heard redodo and litime, but both the forinotrs recommend charging and balancing the batteries before mounting them .... and every six months check everything. So considering this, as I seem to have understood, you can have unwanted effects with an instability of the string. So the balancer for me is an obligation to install it, even if I am not an expert. In the photo, I bought it for the lead, even if it is not a fast balancer, at least it manages to keep them almost in line.
Finally, I don't give it for sure given my skills, in the accumulations of 48v to put them in series there is always a master and slaves to follow, at least I think I understood so!