Is the tank going to be kept fully inside the house with the sump and refugium in the garage?

I think either way, I would look into a chiller....in the long run. Sounds like you are going to walk vs run into the hobby, which is good. If you just start off with fish, you can see what your temp will be at, if you get your tank installed before summers end. You can afford a bit more temp swings with just the fish in the tank. Corals on the other hand do not like big temp swings. I would plan one into your system if you decide to add one in the future. Leave room for one or setup the plumbing so one could be added later.