Tomorrow's setup (in the NEXT WEEK Tab, so long as you do it before Monday’s “week” starts), is indeed available to select your META (difficult vs standard) or normal AQ maps, per BG.
are you clicking on the “META” labeled box (similar to where you have to click on “RAID” for changing your Raids choice during raids week), to be able to select which difficulty of META you want each group to be ? Of course, if you ran any META last time, it should start out with same setup as you had last time (unless an officer has already changed it).
Didnt realize you have to click the small yellow META box to switch, thanks @SummonerNR for the helpful response!