I have never had much success with the old stair tool (especially the create from selection) except for quite simple stairs.
To avoid the steps in the landing you will want to use a slight curve for the path (see attached image).
It may not work still - you might have to adjust the positions of the curve starting point - I kept getting one step in the landing but don't have time to seriously test it sorry.
The shape of the stair can't be adjusted afterwards but you can choose to "edit" the stair (button in bottom left corner of stair settings dialogue), where you can change some of the parameters.
I don't believe the 'L' shaped stair can have a custom angled (I just had a quick look).
I am not very familiar with it as the company I work for has their own custom stair objects (sorry can't share them).
I would make this from pieces and then manually add railings.
It may be tricky to get them to all join correctly though.
This is a perfect example to do in version 21 - if you are thinking of upgrading.
Not that it will be easy there either but it can be manipulated to any shape and the railing can be associated to the stair so will adjust as you change the stair.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11