I agree with the idea of making a swath of grass/path following your existing shapes, and gardening the rest of the space. I also agree with a brick or stone edging. Both those things worked very well for me. I don't have a sidewalk on the outer edge; my constraint is a deep ditch, which forms the outer limit of the garden space. I like the relatively straight line it makes as the edge. You don't have to do it all at once - start with Yard Advisor's corner bed. Get that set up and planted and keep thinking about the rest. Over the following year - or two or three..., you can gradually extend the corner bed towards the house bed, and along the sidewalk. If you do it gradually, it won't feel like such a big change/lot of work but rather like a natural evolution for the space. That's the way I did mine. Initially, I created a big bed in front and a narrow one along the driveway. A couple of years later, a small one was added behind the driveway border where the driveway curves plus another small bed was added in the N&E corner of the property. After a couple of years it was clear that all of those needed to be made more coherent and connected. So I measured a consistent distance from the edge of the main, large bed to eastablish the ribbon of grassy path that ties it all together. The ditch limited the outer ('moat') bed to a very narrow shape but the brick edge gives it more definition and it all works quite well I think. I think something similar would work well for you as shown in Yard Advisors drawing. Here is a link that might be useful:

If you go with a 42" cabinet, you'll be able to use the entire vertical space to adjust shelves as you like. If you keep it as 2 smaller spaces the vertical adjustment will be limited. I'm running into that problem with the 15" high horizontal cabinets I have in our laundry room. I end up wasting a lot of vertical space above the items I am storing because there isn't quite enough space to add a shelf. And you'll lose space with the thickness of the top of the lower cabinet and the thickness of the lower cabinet. I like making our upper cabinet storage as efficient as possible by adjusting the shelves to just the right heights. I would find an unnecessary barrier 2/3 of the way up a nuisance. You'll have to weigh the need for storage vs. the extra expense.

I would want the front window of the DR at least twice as wide. And then put a smaller window, maybe up higher, maybe decorative leaded glass, on the side by the porch. At the last minute I added a small (2'x3') window to our master bedroom just to have light from a second side. Even though I knew it would throw off the symmetry of the room, I love having the light and extra openness that window provides. I can't read the measurements on your plan--what are they for the DR, and the very narrow Study, which looks like it might be too narrow to feel comfortable? Also, why the double doors into the DR from the kitchen? Could you have just the DR between the foyer and garage, with the long wall facing the front, put the study to the right of the foyer, move the J&J bath to the R corner of the house where the porch is, turn and move the BR to the R so the short side is on the front of the house, and put the study on the R side of the foyer? That way, the study would not need to be so narrow, and the bedrooms would be more private as people approach the front of the house, since they would have no windows on the porch. The other BR would now have a window only on the side of the house, and the bathroom (which could use some more space in it) could have a window on the side of the house. The porch would then be along the front of the DR, foyer, and study, between the garage and the BR. Anne

If you love the blue, then a sapphire sofa in velvet would not be amiss.....add a pair of lounge chairs in a bright turquoise, hot pink, bright orange, neon yellow. I think a rug in grey and white would add brightness and block some of the dark flooring. Large modern are with your room colors would be great....it if often suggested on Houzz that large art can be hung and then all the colors taken from the art work an be used to design the room. A lot of white works nicely with silver and cream. Keep the grey but add two colors all over the room Cherry red with black white grey accents Subtle yellow/cream/honey and white Lime and grey and white Tres chic if you like traditional Bright blue sofa with pop of orange.