Not loving black railing at all, what purpose? Not loving posts.

Show the actual house exterior as of now.

Please.

You could dispense with railings altogether if you had steps down to grade from the back door. Railings, especially black ones, are very prominent and make the deck look like a playpen.

The lot slopes to the right so that the fireplace side is much higher off the ground than the left side.

Wood burning fireplace on the deck? If depiction is anywhere near scale and the FP is wood burning, the chimney is going to have to be very tall.

Check with code requirements for railings, it might depend onhow many steps you have and how far the deck is off the ground. If you are not required to put a rail, I personally would do one anyway on any part that steps directly down onto the ground. It's a fall hazard if someone steps wrong on the edge.

Also, pitcures of the house would help as Jan says. I like the black railings but the ones you show are "heavy". Maybe looking at something with narrower spindles or a cable system between the posts would look better. We have black powder-coated aluminum Westbury railings around our Trex deck (against a tan house) and love them.

Thanks to all of you. I have added a photo of my actual house from the back. That old deck is going to be torn out.

Also, the fireplace is gas.

The gabled roof over jut out (4 feet) breakfast room will be replaced by a shed roof. The covered part stops to the left of the dining room window.

Your rendering doesn’t seem to take into account the jut out, the windows or the door shown in your photo. That omission will effectively reduce your floor space under the covered space and really make your fireplace space quite small. Also, does the scope of your project take into account repairing/replacing the siding when the gabled overhang is removed? Have you considered flipping your plan? Extend the deck to the left, past the end of the home about 6 feet. Place your fireplace there. At the right hand side extend the gabled roof outward to the deck edge. Ditch the shed roof. The gable is more interesting. I would extend that section of the decking ( the depth of the deck) further from the house than the lefthand side. This would create some interest and visually create two distinct living spaces with the entry door in the middle.

Thank you. The back is northern exposure, so the idea was to build the porch on the right where there are no windows in order to minimize loss of light. (see real view of home.) The covered area in front of jut out is 10w by 12 deep. The fireplace covered area is 11w by 16 deep.

The shed replaces the gable because

the gable isn't high enough to provide enough height for the ceiling.

Some companies fabricate prefab porch railing systems.

https://porchco.com/store/railings/panels/chippendale-panel/

What you have looks better than anything proposed. You need a professional at the site, I'd get an architect and a landscape designer as well.