Paul_Wilkins gave you a link to a complete guide about centring a couple of months ago. Please take time to learn from the information you are given, rather than ignoring it and repeatedly asking the same questions over and over.
A button of input type="submit" is styled via the UAs internal styling mechanisms (shadow dom and proprietary css). The text is always vertically centred in the submit button by default. You don’t need to do anything and you won’t find any normal css being applied to cause that centering.
Most form controls are styled via the UA (user agent) and many properties are not available to authors.
The two buttons will align vertically because they are affected by the default vertical-align:baseline rules they have. This means that the baseline of the text is aligned in both inputs. It does not actually mean they are vertically centred in respect of each other as that would require vertical-align:middle; (a subtle difference in your example).