Power bank for iPhone 6

Hi all,

Have an iPhone 6.

Looking at this power bank: https://www.monoprice.com/product?p_id=39072

It's rated for more power than the one that came with the phone, and it has Power Delivery.

Wondering if "up to 18 watts of Power Delivery (PD) or 3 amps of charging power" is too much for the iPhone 6 or if the phone adapts to the power being input to it? Also, I know the iPhone 6 doesn't have Power Delivery and the power bank does. Is that a problem?

An even more general question: can any power bank be used as long as it is able to be physically connected to the iPhone 6 through the Lightning connector?

Thanks!