First make sure that you change the document default font to your preferred settings (font and size, in particular). To accomplish that, you can use the Set As Default button in the Font dialog box (Ctrl+Shift+F).

The underlying explanation for these inconsistencies is Word's confusing hierarchy of styles and formatting. For table styles, and paragraph styles applied to text in table cells, to be predictable, the style settings of the Normal style must match the corresponding document defaults (in the Manage Styles dialog box).

Afterwards, also see if the table style itself defines a font. Change it if necessary.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional