Is a third party power bank good for iPhone 12 series?

Power banks will not impact the battery on an iPhone. Your charging cycle may. Never allow the battery to drain below 20%.

Use fast charge with certain iPhone models. You can recharge your iPhone up to 50 percent battery in around 30 minutes.

You can fast charge your iPhone 8 and later up to 50 percent battery in around 30 minutes.1

Fast charging works when you use an Apple USB-C to Lightning cable and one of these adapters:

• Apple 18W, 20W,2 29W, 30W, 61W, 87W, or 96W USB-C Power Adapter
• A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)

If you're not sure which Apple Power Adapter you have, check the wattage on the top or bottom of the adapter:

You always want a cable and charger that is certified for use with iPhones. They have MFI on the box or label.