Hi, I'm also from Germany, as I will immediately prove to you with my English -

If I were you I would never give away Kontakt because it sounds just too good! Kontakt is not only a playback engine, it is also a great sampler, which you can use grandiosely for example in Real Band (and BiaB, see below....).
In Kontakt you have to organize the sounds in advance, of course. But with the new options in BIAB, each instrument has a separate VST instrument, you can e.g. replace a Bandstand- sound by one/ two.... great Kontakt- Sounds- and perhaps even by your own sampled voice - By the way, Kontakt has also small libraries like "vintage", many sounds less than 20 MB.

You can also pre-work with Bandstand in BiaB and afterwards use Kontakt with Realband to let the sound be much greater.

This only as a small supplement. Greetings, Rainer