We have the rail and wouldn’t order the boat any other way. We have our spotters back their when tubing, and older kids love laying back there underway. In Michigan, we have to have the rail to have people back there when underway. Frankly, law or not, I’d require it. I also find it hand to strap items to it (life jackets), or something to grab onto when holding the rear of the boat at the dock, etc. Finally, I prefer the look with the rail on there, but that is probably different for others.
I’ve glanced at how its connected a couple times, but not real closely. It does appear to simply bolt on and off. Due to that, I’d add it to any build, and then at least retain the option of taking it off when you don’t want it.