Those pending charges settle for the same amount. A key exception is the old style USA restaurant chits (still widely used….) that you write in the tip amount. The authorisation is the pre-tip amount and the final settled amount includes the tip…
It pays to retain those chits. I’ve seen places increase the tip amount unilaterally but have disputed the charge and had reversed.
Hotels and car rentals may settled a preauthorisation to a different amount if there were variable charges such as mini bars, petrol etc.
DCC would probably make it harder to understand what happened in those scenarios - as well as pay more.