As I understand, European universities offer two types of Ph.D. programs:
As far as I understand, North American universities do not work in that way.
Is it worth enrolling in a Ph.D. program without employment (#1) careerwise if someone wants a job in academia in future?
Europe is not a country but a continent. The links you gave are from the university of Vienna, and the example of employed PhD students refers to a special program from the University of Vienna, so that is not even Austria-wide.
Enrolling in a PhD program without employment can mean many things, for example it could mean you get no financial support what so ever, i.e. you are self-funded (but even there is variability depending on how much tuition you pay). Being in a PhD program without employment could also mean you receive a stipend instead of wage (which has consequences for your eligibility for social security, pension, health insurgence, etc. This varies to a huge extend from country to country).
In general a PhD degree is a PhD degree regardless of how it was funded. It may be that some programs are more prestigious than others, but that is country specific: It may be that in some countries particular stipends are very prestigious, while in other countries employment is so rare, that getting it is considered prestigious.
I would be weary of self-funded PhD programs, but otherwise stipends and employment contracts are both fine.
