I have a whole pack of Khuli loaches in an open topped tank and no escape artists, as well as a small group of Dwarf Chain loaches also in an open topped tank and no one has made any breaks for it. I love Dwarf Chain loaches, beautiful patterns and active and inquisitive too boot. They are living with a pack of Strebia corydoras and I have never seen any bad behaviour from the Dwarf Chain loaches towards the Corys. Dwarf Chain loaches will also come up and explore other sections of the tank, some people mention them nipping other fish but I have never experienced this in my group. Dwarf Chain loaches also like being in a large group, much like corydoras in the mentality of the more the merrier.
With regards to the rainbow fish you are considering I would go with the Banded Rainbows simply because they are quite forgiving in the water department, meaning they are quite adaptable to gH and pH. But they are really quite a large fish and my Dawson River Rainbow (approx. 15cm) is turning into a real horse of a fish and almost looks too big for the 4ft tank its in.
For shrimps I would either start out with hardy easy to breed cherry shrimp, or go for something larger like Amano shrimp. The downside of Amano shrimp is that they are almost always wild caught since they are incredibly hard to breed in captivity. Any of the Crystal, Tibee or Sulawesi shrimp are going to be more of a challenge and really are better suited to experienced shrimp keepers, they can also cost a lot of money. Gouramis are certain to see small shrimp as food, since they are naturally on a gouramis wild diet. If you do get cherry shrimp I strongly advise only get one colour and don't mix all the colour varities together as they will all cross breed and the resulting offspring are disappointing and generally only end up being given away as culls. Rilli cherry shrimp are very striking and some can look quite similar to the more difficult to care for Crystal shrimp.
