One thing to note also is you can get Economy Plus seats as *A Gold.

Head to the gate a bit before boarding and check the seatmap on the app, if there are still Economy Plus seats unclaimed or even just better paid Economy seats, just mention you are Star Gold and would like x seat, usually they will do it. 100% success rate on US based flights for me, of course the only time I got a no was from LHR to LAX and they were demanding money; while the outgoing flight to London they gave me an Economy Plus seat just fine.