You should use one individual ESC for each T200 thruster. You cannot operate the ESCs with just a switch, you will need something that can generate a pwm signal like an arduino or a servo controller. Even if you need only on/off, you need to be able to generate a PWM signal to control the ESC. Our battery is 18 Amp-Hours, so depending on your usage the time will vary. You can use the current draw vs PWM input (throttle level) charts in the documentation on the T200 product page to calculate some estimates at various usage levels.
Let us know if you need anything else!