Dear marpet,
Thanks for your findings. The java settings in the snap.conf file were already set the way you showed, apparently this is the default of the SNAP installer.
I have tried modifying these flags (setting true to false and vice-versa) and even removing them, but this did not change the behaviour of SNAP on my linux desktop.
Calling SNAP with e.g. modifier “–fontsize 24” increases fonts in the SNAP interface, which helps me for the time being (only icons are very small).