Specifically, I want the default Trim Paths 'Trim Multiple Paths' set to 'Individually' and default Stroke Line Cap and Line Join set to 'Round Cap' and 'Round Join' respectively.
I know I can copy and paste these properties from elsewhere but I am asking about altering the defaults - perhaps in a preferences file? Thanks
No, there is no way to change the defaults. If you have a set of properties that you always like to use, save them as an animation preset.