In addition to feeding problems, I would recommend against BGK and tiger moray since they get far too large for a 75g. You would also have water parameter issues if you keep a tiger moray, which requires hard or even brackish water, with knifefish and elephantnose fish that are from low-pH environments.
Since you're clearly interested in eel-like fish, consider something like an African black knife or brown ghost knife, which are smaller and hardier. ABK in particular is a great knifefish for a beginner. Also consider ropefish and spiny eels, which are also eel-like but relatively peaceful and easy to keep.
Maybe get one of the smaller knifefish and a peacock spiny eel to start? That would leave you some space to pick up another decently sized fish if you find one that you're really interested in.
