I'm a big advocate for just focusing on a single text too, but I know a lot of students who will briefly revisit their other text and just write one or two essays to jog their memory. In the end though, if you prepare well enough, there shouldn't be anything on the exam that surprises you. If there is, then you can rest assured that the rest of the state is probably going to be struggling as well, so as long as you do your best, the marks should sort themselves out.
I'd argue keeping both texts in the air is actually detrimental to your studies too. There's only so much 'transferability' of skills between different texts (eg. general stuff like how to write topic sentences, how to integrate quotes, etc.) and after a point, you should ideally be concentrating on the subject matter of a single text and getting to know it inside out.
If you get to the exam and make yourself choose between four prompts instead of two, there's also a chance you won't be thinking as rationally, and you'll choose an 'easier' prompt without thinking about which is your stronger text.
For your texts specifically, 'Stasiland' takes a bit more background reading than 'Mabo,' but since you'll have to write on 'Stasiland' for your SAC anyway, it's worth spending some time reading through a study guide or even just watching a few youtube videos on the Stasi and the Berlin Wall. If you're already naturally gravitating towards one text, then by all means stick with it, but make sure it's because you know you can write stronger essays about that text, not just because you don't understand the other one. You've go about two months until the exam, which is plenty of time to use your teacher/ this forum/ the internet in general to research your texts, write heaps of practice pieces, and come to an informed decision about which text suits you best.
A choice between two prompts on the exam is usually enough for students to find something to say, and the more 'crazy-hard' stuff you look at now, the less there is for them to throw at you in October
