11 speed on a folding bike? Doable, I`m sure, but doesn`t sound like a good idea IMO. Although I honestly can`t claim any personal experience with paper thin sprockets and high count drivetrains, my impresion is that they start getting finicky about cable adjustment, probably the last thing you`d want if you actually plan to fold it on a regular basis. Though I must admit that I do have one bike with a 9-speed rear and it actualy gives me no more trouble than the 7-speed and 8-speed on the rest of my bikes. Sucks because it robs me of good whining rights
I generally prefer triples since I can`t see any good reason NOT to go that route, but it would be nice to avoid the slightly longer RD on any bike with little wheels. Because I bought my folder with touring as one of its primary purposes, I use a triple on it in spite of the longer derailler.