Installing 3/4 prefinished hardwood and was wondering about the stair railings. I have an open on one side stairwell to the basement, should I
1) remove the railing( they are going to be replaced anyway) lay the floor all the way to the edge of the stairway opening and put the railing back on top

2) mount railing to sub floor and butt floor to it
if so do I need to leave 1/2 in for expansion and install a threshold?

Thanks again for any advise

If your going to replace the railing, it's a perfect scenario to install under it. It's a lot cleaner, and you can allow for expansion under the spindle plate. I would just go under enough so the new plate covers, leave a 3/4 expansion space, and fill over to the wall with 3/4 scrap material. The base plate will then sit flat over the top, and you can trim out the open edge of the plate at the wall.