For 箋 I wouldn't say either way is wrong. As far as etymologies go, double fiesta is the old form of float. If you want to go strictly with Heisig's method then I would go with double fiesta, but if you want to be aware of the history of the characters (how they were simplified) then float makes more sense.

As for 籠 and 篭 they're basically the same character since 龍 is the old form of 竜 so by learning one of them the other one should come for free (assuming you know all the primitives).