Not being an expert I can only give you a modest opinion. It looks like those balancers do only half of what a BMS does. A good BMS will balance but also interact with the charger and monitor and prevent over voltage, low voltage, temperature of cells , and interact with the charger (in varying amounts depending on BMS) Some BMS are set up so you can monitor every cell or combo cells (in parallel at lowest level)
You need one of those balancers for every cell. BMS units usually come in multi cell capability so looking at price vs. BMS - it will be close to the same.
It also depends on what you are converting- If it is a car with a big cell count and expensive batteries I would go full BMS. If it is a bike conversion then taking the chance is not as critical cost wise.
There are also some that say that BMS are not needed and I don't doubt that for them it is true but for me, being lazy and less attentive to details I tend to cover my lack of knowledge and skill with spending money.
You need one of those balancers for every cell. BMS units usually come in multi cell capability so looking at price vs. BMS - it will be close to the same.
It also depends on what you are converting- If it is a car with a big cell count and expensive batteries I would go full BMS. If it is a bike conversion then taking the chance is not as critical cost wise.
There are also some that say that BMS are not needed and I don't doubt that for them it is true but for me, being lazy and less attentive to details I tend to cover my lack of knowledge and skill with spending money.