20 gallon tall isn't a good tank for cichlids generally. They like floor space. What can you get locally. What are your local water conds?
S American dwarfs - apistogramma et al - any will work. 1 pair or a trio. WOn't usually do well in hard water, or high pH.
W African dwarfs - kribs, some others. Prefer soft water again, kribs are pretty durable
Central AM - pair convicts, if you must. Not my favourite choice. Some other that are less often seen. You won't get anything else in the tank
African Rift - shellies, pair Brichardi, dwarf julidochromis - hard water, high pH
Forget malawi