Settings for individual planes over options/planes via the main screen (I haven't yet found another way to change plane settings than via this path) are not used in quick missions.

I have similar issues when in quick mission for choosing the load out.

I saved a particular loadout under a certain name "Angepasst" (=customized or adapted) and it sometimes shows for the particular plane in the quick mission setting screen. I select it without any effect on the load out.

Also saving the load out in a different name: it cannot be selected in the quick mission setting screen as it does not appear in the drop down list of the particular plane

Sometimes this plane only has "empty" load out shown in the drop down list.

I want to emphasize that I did take care that in quick mission it was the same plane as that for which I changed the load out (and paint scheme settings btw).

Also paint scheme settings don't have an impact on what is used during quick mission ...