iPhone X, lightning bolt in my battery.

If it's still plugged in, yes. If it's not plugged in, it won't show the bolt.

Yes. The lightning bolt will appear on the battery icon as long as it connected to power. Its perfectly normal.

It does not mean its continuously charging, and there is no risk of overcharging.

You're welcome. As Phil pointed out, you can't overcharge an iPhone, so no worries at all.