Could anyone explain to me BMS sizing? (for charging and balancing purposes)

G'day, let's, hypothetically, asking for a friend, say I have this setup:

• 72V (20S24P) battery out of 18650s
• 5A/84V charger

What's the smallest BMS I can get away with, only for charging and balancing? Discharge is unprotected (apart from a fuse and low voltage cutoff).

The charger does 5A max, which is well within a basic BMS capability (typically specced around 40A charge/discharge)

What happens at the balancing stage though? Do the balancing resistors of the BMS only have to "overpower" the charger, or is there something more happening?

As far as I understand, top end balancing happens like this: when the battery is charging, as soon as a cell exceeds full voltage, the BMS starts discharging it via a balance resistor. This resistor has to dissipate enough current so the cell doesn't overcharge, for long enough so the rest of the cells "catch up".

Is the max discharging current capacity a concern in my case? If yes, what parameters should I look for in a BMS? Is it max balancing current? Do BMS with bigger overall current capacity also have bigger balancing capacity?

Thanks, hope I explained myself somewhat clearly.