The ESP32 cam board features an ASM1117-3.3V regulator. This regulator allows for 12V input voltage, but also has a dropout voltage of 1V. With only one cell this would technically not even work, as the 3.3V + 1V means we're already above 4.2V of the charged cell. The ASM1117 works well with 5V though, so boosting the voltage might seem feasible.
Let's just say you want 600mA from the 5V source you've just boosted, or 3W. With a charged battery (4.2V) and let's say a perfect, lossless converter you would draw current at 712mA. Looking at a voltage of 3.2V this would mean pulling 938mA.
With two or four servos/motors (stall current needs to be measured), an LED that takes 130mA and an ESP32 with Camera coming in at 180mA - this setup can brownout quickly.
With two cells I hope to be able to power the servos at 6V. I want to later verify, that a 2s cell at 450mAh should hold up longer than a single cell battery at 900mAh.