Aquariums: How to stock my two tanks

Hello,

I have these two tank I have recently set up, a 20 long and a 5 1/2. The 5 1/2 is not yet cycled as you can see by the cloduiness, but the 20 has been running for months, but I added most of the plants recently which is why they're not as tall(i can't wait for them to finish taking over jeje).

Now the thing is I have no idea what to stock them with. I was thinking of a community tank for the 20, but I really wanted pea puffers but after doing further research on them, they seem more trouble than they're worth imo. I know I want to add some shrimp to that tank for sure, but now I can't decide what fish to get, I don't want to be too basic and get guppies. I considered some types of Corys but I don't know how they'd perform in a heavily planted tank?

Now when it comes to the small one, I was initially going to make it a shrimp and snail only tank. I probably won't add anything to it for another month or two because I want to give the plants time to grow on their own and for the tank to be as stable as possible before slowly adding anything. But what is able to thrive in a tank that size? If there's nothing thag hopefully isn't a betta, I'll just conform with shrimp and snails lol.