your talking about a refugium setup similar to what would be done on a saltwater tank. for filtering purpose you need a very fast growing plant. something such as watersprite would be ideal for this type of setup. grows super fast and pulls tons of stuff out of the water column. just my 2 cents.
Is your main tank going to be planted? If so why are you worried about extra nutrient removal? Do you plan on stocking heavily? Sorry to answer your question with more questions
But as far as good filtration plants go, watersprite is only surpassed by duckweed IMO. Java moss does a good job too. Perhaps a mixture of them. Shrimp dont really have a preference when it comes to plants. If you arent worried about maximum nutrient removal then plant whatever your heart desires.