I don't think there are any limits on which desserts you can get. I've gotten the school bread, clouberry horn, viking mousse, and some others when using the DDP/DxDP.
In terms of the side, it depends on whether the entree normally comes with a side (if you're paying OOP). In the case of the Kringla, the sandwiches come with a "side salad" or a "fruit cup", so you would get to pick one regardless of payment method. If the sides have a separate price point, then they are not included on the DDP.
THIS MY FAVORITE EPCOT QS! You get a sandwich, fruit or garden salad, a bakery item, and a drink. They end up being about $20 meals so it's a great value on the QSDP. I recommend either the roast beef or ham and apple sandwich and a sweet pretzel for dessert. My favorite dessert there is the school bread, but it's only $2.69 or something, so it's better to pay for that out of pocket and have two desserts!