Yeah I would stick with upper jaws - if you look at the stickies up top there's one on the species and it separates them out, gives general sizes etc.
I'm not sure on the dimensions of the 90 - do you all think the big 3 UJs could live in there? I am not sure if they would.... Hopefully others will chime in. (Big 3 are Weeksi, Ornate, Teugelsi)
If you went planted african tank, some african butterflies would be cool for the top level. Even if you don't go planted, they at least like some floating plants. Mine will bicker on occasion and the plants break the line of sight to minimize that.
But yeah, some of the smaller SA/CA cichlids could work like sajica, rainbow cichlids, or blue acara.