Could I mix the two or just keep it to one ?
Most but not all of the fish species that will be suitable to a 10g tank with soft water are what we term shoaling (sometimes schooling is used, won't get into that issue) which means they live in large groups of their own species. This need or expectation is programmed into the species' DNA so it is crucial that we have a group. Everyone always want minimum numbers, but it is always going to be better to have more in the group; the more the merrier so to speak. With fewer the fish will be under stress, and this causes all sorts of problems for the fish.
It also obviously depends upon the species. If you were to go with a group of pygmy cories, a group of one of the dwarf rasboras (like
Boraras brigittae, the chili rasbora) you could easily have 9-10 of the cories, even up to 12, and similar for the rasboras. Ember Tetra in place of these rasboras, similar numbers. Floating plants are important for all these forest fish, not only because they reduce overhead light which the fish prefer, but there are incredible water quality benefits.
You could also add a group of Rocket pencilfish (
Nannostomus eques) with the cories and ember tetras/rasboras. Floating plants are essential with pencilfish.
I'll attach photos of these four species.