The .fogsettings file

The file does the same job on both versions, but 1.6 renamed every setting and changed how values get there. 1.5 holds a flat set of keys. An existing .fogsettings migrates itself on the first 1.6 run, so you do not have to rewrite it by hand.

Which version am I on?

Check FOG Configuration → FOG Settings → General → FOG_VERSION in the web UI, or the version string printed at the top of installfog.sh.