Where I work we use Lorann Oils for flavoring candy. It's not the same as beer obviously, but I can tell you that yes, some of the flavors are more potent then others.
On the flavoring bottles they usually have printed how much you should use (as a percentage of the total batch size). I would recommend starting well below that amount and adding more to taste (since you only want a hint of flavor). Maybe even splitting your batch in case you add too much.
Primary 1: Lemon-Lime Hefeweizen
Primary 2: Mock Kreik Lambic
Secondary 1: American Pale Ale
Bottled: Black Magic Porter, Seaside Saison, Head of the Horseman Ale, Cascade Graff, Citra IPA