selecting multiple files and adding/changing output folder

Unfortunately, no; you can't change the output location for multiple files once they've been added to the queue. As a workaround of sorts, you can go into the AME preferences and specify a default output folder; if you do this before adding your batch of clips, all files will be directed there. Changing this preference after files have been added to the queue won't change the destination of those particular files, so remember to do it before setting up your batch.

I've requested this several times: one request was to separate the output path from the file name, so that you change the path for all selected inputs independent of the name (like you can with format and preset), and another request was a dialog asking if you wanted to change the path for multiple files, should you have more than one selected. Personally, I wouldn't want paths as part of presets: if you wanted the same output for multiple clients, for example, you'd have to duplicate your preset multiple times just to change the output location. That could get a little messy, from my perspective, but if you can offer a compelling way to implement that, by all means make a feature request: Adobe Feature Request/Bug Report Form