Hi there! There is no included functionality for rotating the camera using the mouse. It should not be very difficult to add, though. Were you thinking rotation at a fixed angle or more of a free look?
As for simulate, then yeah, that is not something I really use during development, so that there are some errors are unsurprising. I would recommend not using simulate with ATBTT for the time being and just using “play in editor”. I’m planning to look into it and fix it by the next update, though.