am at same strategy too, but pushing one team to 5* and one team 4*
I used to have teams full of young scouts (PT) and 5* 2nd team to play at easy matches,.. but in cup i struggled facing 7*-8* teams (guess was seeded among the token sharks being in top 64 of my server) .. it was a massacre
since then i decided to drop my standard to 5* (got bored of PT tbh) + some 4* subs and just have fun, and suddenly am seeded to lower QT teams who are as good as me, and i started to reach more semi and quarter finals
meanwhile i discovered that financially playing at stronger cup give you better money prizes at each round ..ex: my team was better QT than my friend one, when he show me his cup, i noticed for same level his money prizes were really almost half of mine