16GB should be fine, for most cases. How have you changed the settings.
Have you done something like this?
For the SNAP Desktop application you can increase the amount of memory available to SNAP.
In the ‘etc’ folder of the SNAP installation directory you’ll find a file named snap.conf. Open it in a text editor.
There is the line which starts with ‘default_options=’
In this line you’ll find an option like -J-Xmx5G. Increase the value. You could use something like -J-Xmx13G, if you have enough memory in your computer. By default it is set to ~75% of the maximum value. This is usually a good choice.