RNP AR capability is only available in LNAV/VNAV which is a step back as all other approaches are flown in approach mode (IAN). GBAS is the augmentation system needed for GLS approaches and it seems the original FCOM uses the term GBAS instead of GLS. GLS does offer curved approach path capability, however the 737 is unable to fly those approaches, again due to the limitations of its auto flight system.
MFF means mixed fleet flying, flying two different types intermixed without the need for OPCs on each type every six months. For example on our airbus fleet the pilots fly both the A320 family and A330s. Each check is done on a different type so it is basically A320l, next one A330, and back again to the small one. That is quite different to the common type rating boeing uses for 757 and 767 or 777 and 787.