I had these steep, pie shaped stairs when I lived in an old house in Philly. They were vertigo inducing for a lot of our guests, our dog, and sometimes for me too. I'd for sure get a handrail at least for around the bend.

Limit the pattern on your runner as it can be tricky enough to see the edge of those stairs without getting lost in a pattern.

Look at examples of stairs with a sharp pie turn AT THE TOP of the stair. It is much more challenging to see and navigate the pie turn at the top than at the bottom or on a lower landing.

Look at examples taken from the top of the stairs looking down at the pie shape, not from the bottom of the stairs looking up. Anything looks great from the bottom looking up. From the top looking down is tricky to both make look good and to not make it dizzying.

If you really want some kind of pattern, get stripes on the outer edges of the runner.

For example this is really handsome fabric that I love but it is really dizzying on these stairs because of how steep and narrow they are.

Your window is great. Remember that these are narrow stairs and you don't want to worry about knocking down a mirror or other artwork.

Wouldn’t a mirror just reflect the ceiling as you’re walking up? And assuming your ceiling isn’t out of the ordinary it’ll basically look like nothing? On my own very narrow and steep steps, although not nearly as long as yours, I installed a vinyl wallpaper which worked well for me because I’d often bump into or rub the walls as I was going up and down. It didn’t make the space look bigger but it distracted you from realizing just how narrow it was.

Enlarge the window you have, add windows going down and add skylights above or Suntunnel/Solartube..

Is there hard wood under tha carpet? I always feel wall to wall carpet makes an area look smaller. If you did the runner and upstairs carpet over I would expose a small area of the wood on each side, like in Kendra’s example. And yes to the black hand rail.

The black handrail is too strong and will make it feel smaller. White handrail on white brackets (it’s not feature). Large art at the top. A prettier carpet will be nice but yea you don’t want to create a trip hazard. It has to be broadloom so that will limit your options.

I was thinking something like this stairs runner and would a black rail really be that bad? If so I will listen and go white. Also to the window suggestion, it would cost a lot to get a big window installed so that isn't an option for me. And I was thinking about a mirror there because it will reflect light and mirrors make things look bigger unless any of you have another option?

Also the whole house will have spot lights installed

I'm thinking of doing a runner like this to enhance the space. But worried about the other comment of where it could be confusing where to step where it goes around the corner like in the picture of the stripped runner. It just looks very blank and not sure what I can do to make it look amazing

So you know you have finished stairs under the carpet not stairs designed for carpet? You realize a carpet runner will make the stairs look narrower?

Would some wall panelling look good along the stairs?

A stair runner with a border in this situation will NOT make the stair feel wider. Go for wall to wall. And a non directional pattern or no pattern. And good advice about having the handrail match the walls. Simple is best here.

Just look at that example you posted of the strong border runner. Your eye focuses on the border (which will be extremely narrow in your situation). Just use blue painters tape as a mock up on your existing stairs and see it for yourself.