It’s very simple actually. For two different fonts you will need to do two digital time elements. On one you will set it to be visible only in active mode. (by clicking the eye so it shows in the lower right of the element panel) Then you go to the dim mode and make sure the eye icon does not show.
For the AOD dim mode you do the reverse, no eye in active and an eye showing in dim. The following pictures are of some borders in a watch face I am doing. The left one is in active mode and the right one is in dim mode. You will notice that the eye in the lower right changes for each element.
For digital in active and analog in dim you would do the same by putting two faces and separating them like above to show either in active or dim mode.