VICTRON Battery Balancer

What matters is not the battery capacity, but the number of strings. (A string is 2 or more batteries connected in series.)
A balancer can equalise about 5-10 strings of new batteries, but the more strings connected, the longer the battery equalisation will take.
For heavy battery use, one balancer should be used per 5 strings.

No, the balancer is intended for use with lead-acid battery types only.
Lithium batteries usually have a battery management system (BMS) with an integrated balancer. Therefore, no additional balancer is needed.

SVB note on this
This balancer can also be used for LiFePO4 batteries with an integrated BMS (Battery Management System). It is correct that LiFePO4 batteries with integrated BMS have independent cell balancing, but the BMS only recognises the different state of charge of the individual cells within the battery, but it cannot recognise the potentially different state of charge of two (or more) 12 V lithium batteries connected in series.
In a LiFePO4 battery series connection, it is important that the individual batteries connected in series have as similar a state of charge as possible. If this is not done, the individual batteries will not be damaged immediately, but the full capacity of the battery bank will not be available or the battery bank will exhibit unreliable operating states when charging or under load.

24 V, 36 V or 48 V battery banks often consist of two, three or four 12 V batteries connected in series, which are then charged using 24 V, 36 V or 48 V charging sources. However, these charging sources are not able to equalise the possible different states of charge of individual 12 V batteries.
If any cell in the series connection of 12 V lithium batteries in one of the batteries reaches the "fully charged" state, the BMS of this battery will switch off the charging process. This would then mean that no further charging current can flow through the batteries connected in series and the other cells that are not yet fully charged would not be fully charged as a result.
Cell balancing could take place within the individual batteries connected in series, but the BMS of the batteries cannot equalise the state of charge between the individual batteries. This equalisation can be achieved either with an additional balancer or by giving each individual 12V battery its own 12V charger in the series connection.
It should be noted that a connected balancer is always operable, but individual 12V chargers only work when mains AC voltage (shore power) is available.