well i think delhezis and rope fish will get too big for a 55 so if you use it as a growout you could do 3 sens 2 dels and 1 rope fish
or if you cant upgrade then you could do 3 senegals 1 del
You can add more depends on your filter. They will just piled up anyway. However you need to remove the pleco right away when you add the bichirs. They are not a good tank mates for any ganoid scale fish (Gar and bichirs/ropefish)