Heating issue

You can absolutely use your iPhone while it's being charged. Apple makes no recommendations against this.

Your phone may get warm, even hot while it's charging and while you're using processor-intensive features. As long as it doesn't get too hot to hold or give you a message that it's overheating and needs to shut down, it's fine. Just always make sure that when you're charging your iPhone, you don't leave it under a pillow or blanket or on a soft surface that will impede air circulation.

What IdrisSeabright wrote. I'd like to add that the more wattage you use to charge the device, the more heat it generates (for example, a 20W charger vs a 5W charger). This is completely normal, and your device will regulate itself regarding temperature. As long as you keep it on a hard surface with good ventilation and ideally out of direct sunlight, you're all good.

And yes, you can use iPhone while it charges.

Charge the iPhone battery - Apple Support

___Bubba___ wrote:

What IdrisSeabright wrote. I'd like to add that the more wattage you use to charge the device, the more heat it generates (for example, a 20W charger vs a 5W charger).

Excellent clarification.

It is not recommended to charge your iPhone and use your iPhone at the same time.