Aquariums: What fish do you recommend??

Hello.

So probably next weekend I'll be getting fish for my 20g long. Depends on availability at Petco. Don't have anything else near me. Let me tell you what I've got and what I would like.

I currently have 6 tetras. 3 of them are black neon tetras and 3 that look similar (they don't have red by the eye but near the tail). The lady said that should school together and looks like they all like each other. Also 1 nerite, 1 assasin and 8 ghost shrimp.

The top of substrate is Aqua Natural Sugar White Sand Bio-Stratum. Tank is planted (if needed ill write what plants, pretty standard) with coral driftwood.

I'm thinking of albino cory catfish in a long run after all plants establish good root system. I guess 2-3 months good?? Not sure if substrate is good for them. Is it??

Except that I'm thinking of dwarf gourami, peacock gudgeon, cherry barb.

Second thought is glowlight tetra, pygmy corydoras, dwarf neon.

In my mind but I'm scared they may be to difficult are dwarf cichlids, golden wonder killifish, honey gourami.

I would like to have a nice school of fish to make my tetras happy since they are my original fish. Also at some point like I stated I would like to have some bottom dwellers that would live peacefully with shrimp. I'd like to get my 5g tank a shrimp tank. Probably cherry shrimp. Heard they are easier to keep than other ones. For now I'm getting all the ghost shrimp I can when I'm in the store.

Can you please let me know what do you think of my choices and give me any advice?? Any other recommendations??

Hardness around 300 mg/L. Alkalinity around 0 mg/L. PH around 6.5.

Thank you!!