I vote for some Roman blinds in a nice print or stripe. Something that will embrace all the colors you're bringing in. You may want to check out Etsy. When we were doing our bathroom upstairs, I wanted something different for the window and found a woman there who made valances. Her workmanship was fabulous and I was really happy with the transaction. My favorite thing about it is it's more unique so every other house in the area doesn't have the same thing. A lot of the sellers have pricing that's reasonable too and the choices are unlimited. Here is a link that might be useful: custom made Roman Shades

Yes one long curtain rod. Would you be open to doing a crown molding/valance type thing there to cover up the rod. I think that would look nice. Or maybe a pinch pleat type curtain

I think light and airy is the way to go, and you can do that while warming up the room by the thickness of the material. I’d pair drapes with bamboo or other woven-type blinds or with roller shades. I don’t think it would look odd to have curtains at all because of the step, I’d just make sure the lengths were the same in relation to the floor. You could have the curtain division be where the step is or just treat them as two different windows (separate rods).

I like solar shades for heat and UV control but still allowing you to keep the view. I usually pair them with drapes for nightime privacy but you seem to not require the control so why not just nice full drapes at least 2.5 x the width of the rod and I think if you go with something like linen you have enogh space for stackback on both sides and I would not do the drapes to the corner on the left just center the rod on the window . This is your LR so IMO drapes would be perfect .I do not think blinds are a good choice at all . You have a lovely view the cover on the porch keeps the heat and UV out so enjoy the daytime view and still get privacy at night .