steel grating. It's what we set on window wells where they have to be a part of the patio. Most shops that do iron rails will be able to cut a panel of grating to fit and address the ends. If you want to get fancy and you have composite decking you could even have the grating powdercoated to match. I wouldn't go semi-circular if it's going to be set flush with the decking though. All that'll do is call attention to it. Also more of a PITA to deal with. Keep it simple.

With small windows any light blocked will be noticeable. You can install a frosted privacy film that lets in 80-85% of the visible light and gives you complete privacy. Professionally installed on those windows will run you $150-200 total. You could DIY it with a product from decorativefilm.com. This pic shows an 80% VLT frost film.

Might be easier to cover window from outside with a giant shade or 3 shades - 1 for middle & 2 for sides with window frame hiding separations. Sunsetter makes shades with a solar panel for power that sits on top of shade roller box at top of window. The shades are operated by a remote control from inside the house. The shades can be fully up or down or stopped at any point in between. I have had one of these on a west facing upstairs window for @ 8 years. The best way to control heat is to keep sun from hitting window in the first place. These shades don’t make the room too dark & come in various colors to match or blend with siding. These Sunsetter shades can be made to be manually controlled or wired through walls for remote. My situation was an upstairs window in bonus room on an already built house. This solar powered shade was the perfect solution. Likely this would be less $$ than custom window coverings.

I would put a solar film on the glass above the trim that goes across the 4 windows and then solar shades on the 4 lower parts. They can be adjusted up & down as needed and don't block the view.