Well adding more ram to your system CAN improve performance of you system, but it has to be a very specific case. It only improves performance if you dont have enough ram for what you need.
For example, if your system uses 6 gb of ram, and you only have 4, then adding more ram can improve the speed of your system.
To check how much ram your using, do you normal routine of streaming and recording and edtting and minecraft running all at once, then open your task manger and see how much ram your using. If the RAM usage bar isn't full, then you pretty much have enough ram. If it is at 100% RAM usage, then I would suggest you get more RAM.