I know this is a complicated question, but I've been pretty curious about this and I wanted to see if anyone here would be so kind as provide an answer.
Any input is appreciated.
A republic, obviously. Well, after the Declaration.
How in-depth do you want? The Founders were far from a monolithic group, and what they wanted changed over time. Jefferson and Hamilton, for example, felt differently about the final result.
They initially settled on a Confederacy, then they decided a Federal system was needed.