Most FF plans do not enforce the "minimum 4 flights per year" rule -- exception is BAEC which does enforce it very vigorously. Generally AAdvantage is the best choice of plan, for almost every travel pattern (earn/burn) but there are lots of reasons to use a different plan. I am US based but use QF in order to get US lounge access and to earn miles on BA trans-Atlantic. However Aadvantage is worth about 2x QFF most of the time. I would never give up AA EXP status for any other Emerald.

CX has a lot of competition with QF and BA -- more than with SQ, for example. Despite this CX offers lots of benefits to pax flying their "competition", such as true F lounge access at HKG for QF and BA pax. Contrast this with BA at LHR with their fake F lounge, making the real F lounge (Concorde Room) only available to those flying BA (and QF, thanks to the JSA), but not available to OW Emeralds. BA does a dozen different things to circumvent their OW obligations and to punish pax for choosing to fly a different OW airline and not BA. As an alliance OW really sucks and needs to crack the whip on its members to get more of a single alliance and less of a way to arbitrage self-interest.