For what it is worth-
I have an old Huntington Alloys catalog that lists INCONEL 112 SMAW electrode (AWS ENiCrMo-3) for joining Monel K-500. It did not recommend the GMAW process.
For GTAW, and SAW it also confirmed your idea : ERNiCu-7 , brand name "MONEL Filler Metal 60". (FYI-that is an AWS 5.14, ASME F-42 electrode).