Has anyone had experience with the 'RailSimple' deck railing system??

So, the county plans to pave the space? Do they have a timeframe? I'd talk to the County Planner and ask for his suggestions. You can put forward the position that creating public parking will create more hazard for your property then leaving it garden. And this means you'll going to incure greater expense for the railing. See if they can help or add the railing to their portion of the property.

I think no cap is unique and give a sleek modern touch! Cap is more classic look so can’t go wrong if you do add. 2 good options honestly but I vote no cap

You could do this in a horizontal placement IXI I would remove the middle post of the front porch if it’s decorative. Can you get more pics of the side porch? It looks like a good opportunity to do a nice screened porch, but I also see your meter and an AC window unit.