Lithium Battery Pack - Do I need BMS within parallel connections?
For the most part, putting cells in parallel just makes them behave like a bigger single cell. So, if you take four cells and hook all of them together in parallel, it appears to a circuit to just be a single cell with four times the capacity.

BMS's are built to manage cells in series. Along with current and voltage protections, it monitors each "cell" in the pack to make sure its voltage is within limits, and if any one cell dies prematurely it will cut off the whole pack to prevent the other cells from reverse-charging the dead cell.

Your configuration is "3s4p" - three groups of four parallel cells wired in series. Thus, you need a BMS that can manage three cells in series - a "3S" BMS. Generally speaking, it's irrelevant how many cells you put in parallel in each cell group, as long as all the groups have the same number of cells at similar capacities (i.e. you do not want to put one parallel group of 3 cells in series with a parallel group of 4 cells), since the BMS will see your parallel groups as single larger cells and will manage accordingly.