Thats a logical assumption, but its hard to believe that ay´s v2 power is hold down by a headband, but i think you are right.
I think the only fact why minato is called the yellow flash is because of the FTG not because of his shun shin.
So the credit here goes to ay, who's v2 is able to keep up with the "yellow flash", which means v2 gives ay almost the speed of a S/T ninjutsu.
Look at this scan.
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Back in the days when his squad fought with minato´s, Ay was about to strike minato with his top-speed even though the latter was using Ftg and had spread several markings. Thats why minato teleported to bee, the only direction ay wasn't able to speedblitz at.
Otherwise minato may would have been hit, but we don't know.
I think it is clear that minato isn't as fast as ay by only using shun shin, otherwise he hadn't needed to teleport via ftg.
To come back to topic, without ftg minato definitely looses the first scenario, his shun shin isn't enough to blitz 3T Madara, imo this should be clear, minato is good, but 3T Madara eyes are able to see through every speed and close combat skills minato has to offer.