If you expect to fly 50-100K miles a year for the next several years -- primarily in Business -- but you are looking for a Star Alliance program just because your next few flights are booked with Star Alliance carriers, I think you are cheating yourself. Since your prospective flying will be EU-Asia/U.S. primarily, you would have a lot of options with oneworld from AMS, with either nonstops (PHL, DFW on AA; HKG on CX) or single-connection routings (on AA, AY, BA, CX, IB, QR). You can even earn redeemable miles -- but not status points -- in AAdvantage when flying EY.

As to which FFP to credit oneworld flights to, I would look at AA (but be aware of the changes coming to AA's elite-qualification program in 2022), Iberia Plus, and BA Executive Club. Of the three, only BA requires that you fly some BA- or IB-coded flights to attain status; neither AAdvantage nor IB Plus has such a requirement. AAdvantage is notable for not collecting carrier surcharges on award tickets, unless you are flying on BA or IB.