How to make a Wizard of fixed size with pages that can be adjusted to dialog size

I have a class inheriting QWizard, and I have many independent pages inheriting QWizardPage, each page has a layout with FixedSizeConstraint, UI of these pages were generated by QT designer (All page are of the same size at beginning).

I hope the Wizard has a fixed dialog size, and the pages can be adjusted to the dialog size. On Win and Mac, the size of wizard dialog is not the same, however, both of them are larger than all the initial page size. But after it run I didn't see the page was adjusted to the dialog, nor did they keep their original size, the layout is so bad. So, how can I get a normal look of the Wizard? that is, the page extend/shrink to the dialog size, like it is a standalone application of that size. I will add logo and watermark to those page, I hope they would never become worse.

Any of your advice is appreciated.