EMT all the way, or start with IMC outside and transition to EMT inside the building?
Sorry, there are no single solid answers to most of your questions.
To transition from IMC or RMC to EMT usually we just fit together a rigid threaded coupling and an EMT  connector. They make a fitting that I never used, but have heard rumors that some AHJ's require them. Some of that problem can be avoided by using an LB outside where it enters the building, which also eliminates the sweep question. Just be aware most LB's are internally marked at a maximum wire size (for bending radius) that is less than maximum conduit fill.
It is a lot easier to cut EMT to the exact length you need versus trying to miss structural members with threaded pieces and sweeps. Rigid/IMC should nearly butt in a coupling, but it doesn't always seem to measure out that way.
On the other hand a raintight EMT coupling is at least 9 pieces, that don't fit together well, and a couple of those parts are easily damaged, wasting the whole part.
I would seriously evaluate the size of conduit you are running, 2&quot; could be overkill, and complicate fitting and increasing cost with little benefit.
1.5&quot; conduit will get you 3@3/0, even aluminum will get you single phase 175A.