Well... power consumption varry between sensors, they are not too high.
Also, it depends on the way you use these sensors.
Most of them can measure constantly in configured periods, and tresholds, and assert an INT line if they detect something (most power hungry).
Or... include the measurement cycle in your main loop on the ESP, or in certain time intervals, so it will do the measurement only in that cycle, and in every other time, the sensor is inactive, consuming near to nothing.
BTW, the VCNL4100 and VCNL4200 are waaaaaaaaay to big, and you should only use them if you sense something a meter away (VCNL4100 can detect 1m distance, VCNL4200 is for 1,5m distance).
Most sensors are OK for you, they are small, and are designed for 200mm distance, they have low power consumption. These are the sensors, you can find in your smartphone, which will disable touch and display backlight if you put it over your ears... so they are somewhat low in power consumption (beacause they are used in smartphone)
Science stuff: The way capacitive touch works, is that the metal plate which is the sensor in most cases just connects to a GPIO pin, and since the circuit is not closed (metal plate hanging in the air), there is no current flow, and nothing happens.
If you put your fingers on it, your fingers (since it's conductive), and the metal plate will act as a capacitor. Capacitors like to charge up if voltage is applied, so this starts drawing current from the GPIO pin to charge it up (your body acts as a good capacitor - regardless of your body weights of course
).
This small current that is drawn, is what gets measured by the ESP32 and gets interpreted as a touch.
Capacitor halfs need to be relatively close to each other to work, and also need some insulation (thin plastic, or solder mask on a PCB). (a parallel homogen electrical field must be present between the 2 halves, if charged). The capacitance of a capacitor decreases by the squared of distance of the 2 halfs (considering the area of the 2 halves are constant), so the further away you move, the less likely your finger or body will act upon the sensor.
Rule of thumb: The further away your detected object, (depending on the dielectric constant of the insulator), the bigger the metal sensing plate must be.
You need a very big sensor, to make it work for large distances... (in theory, 10s of cemntimeters) which is far from practical.
Regards,
Vader [BEN]