I would agree with you about softer BH rubber.
As you develop your strokes you're going to find that a softer rubber will likely work better on the BH, simply because you cannot develop as much power from your BH swing as FH swing. You just cannot get into/activate harder sponge on BH side, which you can on FH side due to the greater power of that swing.
Regarding your suggestions, I think they look pretty solid but any TT website will assemble the best for you if you ask them so you don't have to be married to Butterfly.
As you're in the Balkans, I will mention that I have bought from
www.tt-store.eu (in Bulgaria). I have no affiliation with them other than 5 or 6 purchases and they've always been great.
They don't sell Butterfly but might be an option for you if you decide on something else.
For example
Blade: DHS Hurricane H-WH with Rakza 7 MAX on FH and Victas Ventus Limber on BH. ~€100
Or
Blade: DHS Hurricane H-WH with DHS Hurricane 3 Neo on FH and Rakza 7 or Victas Ventus Limber on BH ~€120
Just more food for thought 😊