You need to decide what you want.
You seem to keep changing your mind with every suggestion.
You can't keep a GT with another smaller cichlid in a 75 at least not long term, as when it grows up it will kill the other fish.
A blue acara or a Electric Blue Jack Demsey or a Jewel are good options. You could try a combo of any two of these fish, but you will need to provide hiding places for them and also keep a small tank handy if the conflict gets serious and be prepared to return one of them, if they start to have serious fights.
A few bichir experts seem to think you can keep a couple of them in there, so you might be able to do Bichir with a cichlid or two, but then you will need to have good filtration (biological and mechnical) and be regular with your water changes.