Altums are easy distinguished from scalares. Look for the sharp indentation above their eyes and brown bars. Fins should be erect. Your tank fits for both species.
I'd go with the binlids(discus) then.
By the way, if you want altums, then no cardinal and neon tetras for you.
Altums have extendable mouths and will eat even the adult harlequin rasboras.
Discus isn't that difficult to keep. I know it's expensive but they can be rewarding to keep. Trust me, you'll be a discus enthusiast once you own discus. And perhaps, breed them successfully.
Malawi cichlids? I'd ditch them to the bin. I used to own them but I'm disappointed with keeping them as they poop alot and worse, when they grow, they can bite and their bites are painful. No plants for the tank either. If they eat javan ferns, then they have high chances of endangering their lives. One article mentioned that scats eating javan ferns tend to die sooner than those that did not eat that plant. From my understanding, the reason why some pure vegetarians avoid this plant is that they contain poisonous substances.