I just ate at both places two weeks ago. Non-alcoholic soft drinks (and milk for my DS) and dessert were included at LTT. Biergarten had desserts on the buffet - not too exciting - apple strudel, tiny pieces of black forest cake and something cheesecake-like. Can't remember for sure about drinks since I had a beer but I *think* DS had lemonade. I know I wasn't charged for it. I don't think I've had a Disney buffet that didn't include desserts and drinks. Maybe a plated all you can eat like Akershus doesn't include them, but the full buffets seem to, in my experience.
As for your question re: meal plan, I am not sure. Hope you get the correct answer!