16GB is already a ton of RAM and most things would only use up around half to 2/3rds as much, so between 8-12GB RAM. Unless you are compiling massive amounts of data I don’t think you’ll see much of a benefit, if at all, from investing in 32GB RAM. 16GB RAM is already more than enough for basically everything and that’s enough to hold a ton of data in memory.
The only thing you’d really benefit from if you already have 16GB RAM is a faster CPU/GPU/SSD. I don’t think you’d benefit much at all past DDR3-2133mhz as 1600mhz is fast enough for most things. DDR4 may have a fairly significant performance improvement but that is offset at least for now as although the DIMMs have the capability to reach in excess of 3000mhz the downside is increased CAS latency which should get better as DDR4 reaches maturity.