Close in the arch and replace the columns. What style is this house? A more contemporary or model railing may help the stairs but may not flow with the house.

The kitchen was remodeled in a completely different wood...so at minimum thought I'd stain stair rail/treads to match. House is fairly contemporary. No other arches to be seen.

I'd leave the arch, but get rid of the columns and the horizontal bar? Beam? Piece of wall? That holds them up, which would leave the open feel they're going for if you like that "open concept" thing. Unless it's structural. Filling in arch makes a lot of blank wall.

So if the columns aren't structural then I would open the whole thing up, squaring it off to the header. For the stairs perhaps iron or metal balusters would give it more visual appeal.

Better check on the weight of that arch before you remove columns. Actually the columns are out too far and should be next to the wall .