It literally just lets her have more than one set of fans summoned at a time. Like, technically she has dual fans -- one for each hand -- and can dismiss them, but if, say, she was fighting and dropped one (or had it knocked out of her hand), she could just summon a third and leave the other one sitting there without having to dismiss or collect it immediately. And they all function the same as normal...

And it already extends to Ichizaka's shields when she's fused with Gongenzaka... So I guess the question is whether Darcie could duplicate the tanks, too? And if the tanks or brush are linked to the ink generation?

If they did this, Darcie'd probably have to serve as judge, because it wouldn't be fair for somebody who can jump from one color ink to another without any penalty to compete...