I'd personally stick with a standard 8ft pointer ladder, they have quite a wide base and are very stable.
The extending pointers are ok, but you can end out with only room for one foot in the uppermost rungs.
On the ones I used in the past you could remover the pointer section, but because of the nature of an extending pointer, they are quite narrow and so not as stable, you are also not going to have the angled rubber feet on the bottom of it.
some love the extending pointers, but I'm not one of them.
I think you are safer to use a standard pointer and a light trade extention ladder for the upstairs work.
Ian