Hi there
Sorry, but I have no answer on the themes aspect. It may very well be that is all the themes offered. As for things being disabled because they aren't part of a trial version, that would not be the case. The only limitations of the trial are that you cannot use it beyond the trial period as well as anything you create won't be usable after a defined period of time.
Perhaps if you could share a screen capture of what you are seeing we might offer more. At first, I thought perhaps drag and drop would be maybe disabled because it's a responsive project. But I just created a new responsive project and see that I'm able to launch the drag and drop wizard. I'm wondering if perhaps this was not available in the first round of Captivate 8 and became available in a service update. Have you tried clicking Help > Updates and ensuring you are updated? Maybe that's all you need to do.
Cheers... Rick 