White Raccoon Mario can't use Gold Flowers and can't touch Koopa shells without instantly killing them. Those two will severely limit your ability to get big coin amounts on most levels.
It is possible to get 30,000 coins with White Raccoon Mario, at least on the coin-farming DLC packs, but any other level pack is going to require a Gold Flower, and often some shell-jumping trick or at least kicking a shell, for a really high score.
But there's really no good reason to get a million coins anyway, so do whatever's funnest.
Oh hey, I have a question: If I've set a DLC pack as my StreetPass record, what happens if I StreetPass someone who doesn't have that pack? Or vice-versa? Can the person who doesn't have the pack see the record? Can they challenge it without having bought that pack? Will it even show up as a StreetPass on their system?