Welcome back to the Wefugees Community and thank you for your questions!
The residence permit according to section 25b of the German Residence Act is "granting residence in the case of permanent integration". Compared to, for instance, the residence permits according to section 25 paragraph 1, paragraph 2, paragaph 3 etc. (in which the respective holders have different rights/some paragraphs are indeed "stronger") you can not read the different paragraphs in the 25b in the same way. Section 25b paragraph 2 is mentioning the reasons for rejection, for example. Paragraph 4 is issued to the spouse or children of the person who holds the residence permit according to section 25b paragraph 1.
To sum up, if you meet the initial requirements for the residence permit according to section 25b, you will be issued the 25b paragraph 1.
Coming to your second question: If you are holding the 25b and you are not already married, you can, unfortunately, not apply for family reunification. My colleague Éanna gave some details on this here. And even if the couple was already married, the family reunification with this residence permit is only granted in very exceptional cases.
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,