Issue: You are technology group X with unit type X but you can select a wide range of units that you should not normally be able to.

Example: You are Ulm but you can select Japanese Sammurai Cavalry.

Solution:

In EU4 1.17 unit type is tied to technology group
To create new unit types I had to create dummy technology groups
Without those defined the game thinks that the units are available to every tech group so they populate.

If you are experiencing this issue it means that you do not have Westernization Reworked, have an old version, or are attempting to use this mod without WR and without the supplied patch.

Get the new version of WR or use the patch and you should be set.