As above. But just look in the memory pressure graph of the activity monitor, assuming it was struggling before it should no longer struggle. Otherwise RAM makes diddly squat difference to the speed of a computer, that's dependent on the CPU.
To add another explanation because why not. CPU calculates everything, so the faster the frequency the more calculations it can do per second. Whilst working it puts data into the RAM, like a working out sheet; so the more RAM it has to work with, the more it can put floating variables into and use it when it needs it. The storage device provides applications which give the CPU instructions, so the faster the storage the quicker this is able to send and receive said instructions. A fast CPU and SSD can manage with very little RAM, RAM is more important in a slower machine or when physically blocking RAM in cases such as virtual machines; or running serious CPU calculations such as renders.
For this reason you cannot measure any performance difference as it doesn't directly make a difference. If the system was struggling before then adding more RAM will reduce CPU stress and artificially provide greater performance. However if the system wasn't stressed before then you won't notice any meaningful difference besides battery life.
Good luck!