QLC drives are all trash. They have ok performance in bursts, but the sustained performance is terrible and the reliability is awful. 

QLC means it’s storing 4 bits of information per cell. And it does this by holding a charge at 1 of 16 levels. It’s basically analog. 

The only way QLC achieves decent burst performance is that they all have an SLC cache. SLC is a single bit per cell. 

With the current tech, I wouldn’t go beyond TLC, which is 3 bits per cell.