Corys are fine unless you are trying to breed the GBRs, I understand that you may not prefer Corys. Amano Shrimp, Amano Shrimp, Amano Shrimp. I purchase both regular Amano's and XLs. https://aquahuna.com/collections/fre...s/amano-shrimp
Pest snails. After purchasing different snails, all very nice, and having others come in on plants, etc, I am going to let my snails come to their own natural balance unless it is an aquascape display tank that will only have nerites in it.
I would also add Otto's into your clean-up crew.