HOW TO CHECK IF YOUR SMARTPHONE COMES WITH BATTERY CHARGING CUTOFF TECHNOLOGY?

Use the charger that came with the handset, charge your smartphone and see what happens when the handset gets fully charged i.e. battery is 100%. If you still see the battery charging icon and/or if there is LED notification and the LED is on then the smartphone does not support cutoff.
Ideally with cutoff tech the smartphone charging should stop at 100% even when the power is connected.
Now if your smartphone does not support cutoff it would make sense to stop the charging process once the battery reaches 100%. Doing so will improve battery life and health. And if cutoff is not supported better not put the handset on overnight charging.
Now you can use a power bank effectively in case your handset does not support cutoff. For this you need to use power bank with battery that is near about the same capacity as your smartphone for example if you smartphone is using 2000 mAh battery go for power banks that come with 2000 to 4000 mAh battery.
The idea is by the time your smartphone gets charged to 100% the power bank batteries will also get depleted. Once the power bank battery is exhausted the charging will stop.