This is a complex question.
If you've got soft water or hard water... this will impact what you want.
Cichlids can be bossy turds, or can mellow out and it all comes down to how they're stocked and chosen.
You don't mix south american Cichlids with African Cichlids. Stick to same region. And carefully research the area you want to do. For example, you wouldn't put Lake Malawi Cichlids in with species from the Congo, even though both are from Africa. Totally different water parameters and behaviors between the two.
Some of the south american ones are much more peaceful, such as the rams. Or can go larger species. Many of the geophagus are nice too, but will need certain conditions as well.
A good mellower cichlid for a 75 gallon would be a nice group of blue acara, and leaves you options for some upper level community type fish, such are larger tetras like diamond tetras, skirt tetras, emperor tetras, etc. But, these will require softer water, so that's something to check into.
There are also apistogramma species which are neat, though small. Some have more fussy parameter requirements though too.
From congo there's kribensis and jewel Cichlids, plus a few others I'm not well versed on. These guys would do well in softer water, similar to some south american water range.
If your water is liquid rock, look into any of the rift lake Cichlids or central american Cichlids (convicts are one such cichlid). But do not mix them. A petshop does not reflect longterm thriving conditions to mimic