Is there a view, say of the sea or mountains? If so, often the sofa is arranged to take advantage of that. If not, it doesn’t matter.

If you plan on having a TV, mount it on the wall or set it on a console across from the seating.

Often the dining table is near the kitchen.

I like your ideas. I find in this space where the big furniture goes is the easy part. It's what you do with all the dead space after you make that choice. I've had the couch exactly like you've suggested before (I have a small lake view which is extremely nice) But what ends up happening is I have that cubby section about 90" wide and 30' deep empty. It's physically off center from the window and your eye is naturally drawn to it when you look over into the living room. What's your gut instinct with focal point?

I’d put a sofa in the alcove. Tv in the corner. Small drop leaf table on the ‘welcome’ wall. You’ll only pull it out for company.