Definetlly would not put discus in there. red tails start fairly small, but yes they would fit well since they have lil barbels and lil mouths like the elphant nose they would look amazing in here, You can get albino and glofish red fin sharks too!
If i remeber correctly bichir are predators so if you get that becarefull with red tails as they will go in the mouth like ramen noodels, congos would look stunning in this heavily planted tank no matter what you decide on putting in congos will look good
https://www.aquariumsource.com/elephant-nose-fish/ Im guessing you looked at this site although it lists discus discus are beautifully fish in planted 75s but I just feel they are subject to attack by ammonia and bichir bites but its possible it could work.
If you go the birchir route you could go with a really nice center piece fish like a flowerhorn. You could try oscars but you have to make sure enough food reaches the bottom for the birchirs.