I'm not going to attempt a full answer because I have to conserve my brain cells for working in the remaining wee hours here. Briefly the higher the bit rate means you have higher "headroom." This is essentially room for error that will remain inaudible or less audible. The resulting signal will be cleaner and "better."

Also the equipment itself manages signals using larger "words." When effects are applied, or multiple signals rendered out to fewer tracks (mixed down), the internal processing might be 20bit, 24bit, or 32bit (relative to 16, 20, 24bit output or record signal). This added word length is used only in the processing. The higher the bit-rate the larger this additional space must be, in order to maintain the quality of headroom. All very specific to your equipment.