but then there's 2 mischling thats always out and about, param. affect each shrimp differently?
Yes, and at different rates. Mischling are hardier than BKK, so what can kill a BKK may only phase a mischling. I think you probably should set up at the very least a 10 gallon tank if you are experienced with CRS, or a 20 gallon tank if you are new to CRS. It will make things a lot easier for you to control and observe.
I have 5 years of CRS experience, and I would not dream of using a 5 gallon aquarium. It is too much work.