It recommended to use MAM on Cambridge because it can be guaranteed there is nothing in there that will adversely affect the plan, so i would say best to stick to MAM if you can
The ingredients on mix-a-mousse states it's just gelatine powder, so surely it's exactly the same as gelatine powder bought from a supermarket, just way more expensive.
Well ive just made some jellies with water flavouring and gelatin and they taste great. used a pint of water a packet of powdered gelatin and a teaspoon of flavouring. ive made them in some plastic cups so i can have them over the next few days.