Enough is enough. You are ok on ram.
Windows keeps code around in ram in anticipation of reuse.
The real metric is the rate of hard page faults which should be minimal, if any.
Nothing wrong with 16gb, but it is probably not that helpful.
Check your pc for malware.
If you do not have a ssd for the "C" drive, you will be very pleased with the improvement in all around quickness.