Not directly related to Nazis specifically but if you're interested in the topic of Finns and whiteness, I've been meaning to finish this article by a historian I follow. She studies ethnic groups that were located in the peripheral/interstitial regions of empires, such as Finns and Tatars.

Imperial Complicity: Finns and Tatars in the Political Hierarchy of Races (pdf)

I seem to remember reading somewhere that in their post-war plans the Nazis considered Finns too Asiatic to be allowed entry into the Reich but planned to keep them around as a useful buffer between Aryans and the Asiatic Hordes

On the other hand I think some Nazis had an interest in old Finnish mythology, etc. Fascism and Nazi race science are completely incoherent anyway, you'd probably get different answers from the same Nazi based on which foot he stepped out of bed on that day, or the phase of the moon

There's a really odd essay by British-Jewish historian Cecil Roth from the 1930s where he tries to proves that Jews are Europeans and he's like "actually, the word "Europe" is from Phoenecian and Jews are more European than Finns and Magyars