preserve font stlye but change font and size

Word and InDesign document can have the same named paragraph (and character) styles. Same name but differing attributes. When same style name meets same style name, the text imports but changes to the InDesign document style appearance.

Furthermore, where style names differ, you can File > Place … with Show Import Options turned on, and also explore Style Mapping one style name to whichever other in the InDesign document.

Assuming you’re placing a Word document, be sure to show options when placing it. Make sure to enable Preserve Styles and Formatting from Text and Tables.

If you don’t have them already, create paragraph and character styles. Then perform a find change operation searching for bold and replacing it with the bold character style. Do the same for italic.