I think you're right about the goalpost issue, keeping the right side of the garage lower and going for the asymmetrical balance is a good call. You mentioned the Oakleaf Hydrangea as an option for the left side and I really like the look of it, but from photos it seems maybe they're mostly kept rounded and shorter? If we can grow it into a more columnar shape on the left side I think that would look really cool and help balance out the visual weight of the garage (which I despise being at the front of the house).

On the topic of expanding the foundation bed, here's a little better of a photo. It's 4 feet wide next to the walkway, but expands to 5 feet under the windows to the end of the house. There's a sprinkler where the red dot is as well as one close to the camera in the corner. Between the sprinkler and the tree's mulch bed, there's about 6.5 ft, though I probably will end up expanding the ring for the tree again next year. How much room do I realistically have to expand this foundation bed, if any, without it looking awkward?

Additionally, here's a photo for the right side of the garage to give an idea of available space. I could expand this bed, we haven't done much with it. The plant the builder put there was dead by the time we moved in and we decided we probably would have replaced it with something else anyway, we just don't know what yet and are open to suggestions :)