Is there a way to bold a word within a Material-UI Typography element within a Card without a shift on render?

Have you tried with Box component?

You could do something like

<Typography component="div">Normal text <Box fontWeight="fontWeightMedium" display='inline'>medium font weight text</Box> and some more normal text</Typography>

Note that component="div" prop on Typography wrapper is required as Box component cannot be nested under the Typography’s default p.

Source Typography font weight