What is the update you are planning ?I mean the style and maybe that would help with the join up part. IMO it seems fine to me as it is with that style railing.

Here's a picture of one where they put a post at the turn. I agree with Patricia that it depends on what style you're switching to as to how it's done.

Transitional Metal & Wood Staircase · More Info

It has to join in some manner- what you have now is incredibly non code compliant which is fine until you touch it and then it all has to meet code.

I like Kendrew’svexample.

Yours looks like it belongs outdoors.

You could keep things simple and just paint it all black.

Do something on the back wall so the mirror is more prominent.

Join

Join it, looks disjointed lol

The width between spindles is not code compliant. I would rework in black metal to code and join the upper and lower levels with a continuous rail.