A full mileage redemption will not affect your seating options, although asking to be seated together could potentially affect your options, though with MMB online you shouldbe able to adapt as required.

For some reason LAX availability is shocking in J, particularly at weekends, but OK in F; SFO is much easier in all classes if your dates are inflexible.

Remember with an Amex 2for1 you can fly out in F and return in J – well worth it for the 25k extra miles it costs (125k total), and you are awake on the outbound to experience F and asleep in J on the return (plus IMHO catering, well rested crews and F/Concorde lounge facilities are better on the outbound). You might even be able to open jaw and fly into LAX and out of SFO (always prefer it this way round as LAX is a horrid airport to have to rush to in heavy traffic to catch your return flight).

I was only asking about the route you are taking to ensure you get on a 747 so you can get an Upper Deck seat, and to suggest you consider flying ex EUR to maximise tier points and possibly reduce the cost, but ExEur is not possible on Amex 2for1 and tier points are not releveant to your plans.

As ever, if trying to snag 62k and its neighbouring seat as a none-Gold your best bet is at OLCI 24 hours prior to boarding.