Hello @Arkaedus
First up welcome to SKFA.
There are many ways to do what you want. The first decision is are the dividers are going to be glass or acrylic.
Both have their advantages and dis-advantages. Glass is stronger and is easier to stick to glass so it will help with the strength of the tanks. It is harder to work with. Acrylic is not so strong and cannot be relied on to stay stuck to glass with silicon so should not be part of the tanks bracing but it is much easier to cut.
So first up you could cut holes in the dividers and cover them with a small enough mesh so the small shrimp cannot go through.
You could cut the dividers 4-5cm short and have some mesh at the top so the water flows over the divider and through the mesh.
You could cut the dividers 4-5cm short and have the gap at the bottom. Cut some aquarium safe foam (filter foam) 6-7cm thick and compress it into the gap so there is no open holes. The water will flow through the foam but the small shrimp will not be able to go through. This will also add mechanical and biological filtration to the tank.
All three have their pro's and con's.