Will the detached garage be visible from the front or completely hidden? To me that makes a difference. If it is visible from the front of the house, it is better if the two sidings match in material, style and color. If it is completely hidden from the front, then having a coordinating vinyl works IMO.

Visually, you definitely don't want that narrow recess on the front of your house. I would add to Virgil's and PPF's suggestions that, depending on the style of your house and your climate (as in whether you think you would ever use it) you could also build an exterior wall between the garage and your bedroom, add a patio door somewhere and have a private courtyard off your master suite with a garden view from the tub. Then you wouldn't need the blinds closed in the bathroom all of the time to retain privacy. I know someone on this Forum who is adding on to their Mid Century Modern house has one of these private courtyards.

There shouldn't be any water going toward garage. All should be running away. If that's the case, the garage is either built too low, or the grade surrounding it is too high. Obviously, this can be a major challenge to fix, but the plan outlined here, of cutting the drive, is not going to fix this problem. This looks like a solid masonry garage. If it is, the real fix is probably going to be to repour the apron, raising the threshold level a few inches and pouring a new level of garage floor. This would entail shortening the doors and trim correspondingly.

A rectangle garage is “simple” enough, that if you’re not looking for detailing your match the house, then you don’t need an architect involved. But, if you do want a building that looks great, and echoes the house detailing, an architect can help you with that. Does he have a transit and can measure the future site? Because “flat” isn’t usually flat. That’s the biggest issue that people don’t realize, until they try to fit garage plans to the actual site . Garage entries need to be at grade. If the ground slopes away, you’ll need compacted fill at the rear. If it slopes down towards you, you’ll have to remove dirt and degrade to keep water away. Siting the garage needs that information, as well as required setbacks, utility paths and easements, etc. Even a simple rectangular garage can end up pretty complicated to build unless your on a large dead flat lot, with no utilities interfering with anything. Which brings us to how you plan to get electrical service, or any other service, to the garage. You have to figure that out too. Find a good local contractor, and talk to them about what you hope to achieve. The more time and money you spend with a pencil in hand rather than a hammer, the better the job will be.