Re Reenactors with Shield Designs from the Notitia

[Flavivs Aetivs]

I don't think so, if they say auxilia they mean auxilia. vexellatio means part of a unit, and it could of course have been a vexillatio of an auxilia unit. But we continue to find old-style infantry and cavalry units named cohort and ala, etc., so I wouldn't worry about a unit named 'auxilia'.
On the other hand, you may be looking at part of a new-style Auxilia Palatina unit?

I doubt it. If the Notitia was updated until 425 then any Palantine units would have been recalled to fight the Goths and the invasion of 406 and all the usurpers of that era. If it was updated until 435-442 (I have a theory that it was, I will explain later) then the auxilia palatina units would have either been recalled or paper units (not existing IRL)