Valley fighting. Agni should do their best to take a good vantage point, find their Fujin opposite, and set up a trap (such as lighting a fire in a deep box canyon). The goal is to pin the Fujin down into a one-on-one fight in clear terrain, which favors the stronger Agni. Fujin, on the other hand, should use their fast-moving ability to get a sense of the land before searching for the Agnis. Given Agnis ability to see heat, Fujin should assume their position is known, and therefore figure out ways of drawing the Agnis into terrain that'a favorable for the Fujin (lots of stones, wet wood, or dust).
Dojo fighting. Fujin should favor steel nets. Because of Fujin wind powers, they can manipulate these area effect weapons at a distance, rolling up the net into a whip (possibly with hooks), or capturing and restraining an opponent for a killing blow. In a close fight, these weapons allow the Fujin to control most of the field. Agni should favor smoke bombs. Agni can use their power to set the smoke aflame, stripping the air out of the room and simultaneously stunning and weakening a Fujin opponent (who can't draw breath to use their power). The air blast will also most likely snag a net, making the Fujin weapon ineffective.