As usual, John Frawley has some very rational observations on the Nodes:
"The Moon's Nodes do not cast aspects, nor can they have aspects cast to them. They affect planets only by conjunction. A planet conjunct the North Node is helped, strengthened or increased. A planet conjunct the South Node is harmed, weakened or decreased. Which of these meanings is relevant will be clear enough in context.
If one of the Nodes falls in a house relevant to the question, it can affect that house. The North Node falling in a house is good for the affairs of that housse, or shows the querent benefiting from that house. The South Node falling in a house harms the affairs of that house, or shows the querent losing through the affairs of that house. The effect is much more marked if the Node is close to the cusp.
Be careful to avoid dragging them into judgment unnecessarily . . . the Nodes will appear in every chart, but in most charts they have nothing to tell us. If one of them falls in a house that concerns us, we can take note of it; if the Nodes fall in houses that do not concern us, there is no need to rack our brains wondering what those houses might mean. Just ignore them."
Frawley doesn't give any exaltation to either Gemini or Sagittarius. Other writers give them as you say (but with the South Node in its fall in Sagittarius); these writers are not specializing in horary. William Lilly, on the other hand, shows both Nodes in the "Exaltation" column of his table.
(From The Horary Textbook, Apprentice Books, 2005