Need to run a mobile robot on batteries
Define Efficiency, Features for Active or Passive Balance, cost, complexity, time budget,  spare parts , temperature rise, thermal design of each block in addition with electrical design with max load while charging and operating.  ( which could be almost twice the 1C current rate or ~ 6.7A  !!  and that BMS chip is limited to 1.5A)

So ALWAYS start with Specs before you waste too much time.

Battery background https://www.digikey.com/en/ptm/t/texas-instruments/introduction-to-battery-management-part-1/tutorial

If starting power at full voltage is  0.8A*12V = 9.6W per motor. 

What software restrictions limit 5 motor starts at full acceleration?

I suggest you have PWM control V/f of motor slew rate controlled to limit current which will also improve stability.

Assuming you have done this and peak power is 18W with 2 cells at 3350 mAh typ each @ 3.6V =  12Wh * 2 = 24 Wh max then your max load will be slighly more than a 24/18 = 1.33C load rate. Which seems reasonable for experimentation at max load.

Batteries will be very well balanced (&lt;&lt;1%) when fresh and degrade very slightly then exponentially before EOL (end of life)   Meaning that charge balance by cell monitoring is necessary for internal charging.

Try to keep between 20% and 90% State of Charge by useage. 90% is shortly after going from CC mode to CV mode.  But if you have a good BMS chip, follow their advice. I only suggest smaller DOD range to extend battery total Wh*charge cycle life span. Using 50% will double battery life capacity.

Using a good Full MOSFET bridge with a good BMS and good software for slew rate control helps on the servo side while braking also recycles charge to battery.  It depends on your requirements.