Widget inputargs, what types am I working with when it comes to lists and attributes ?
Yes, if it is in the name of an attribute
Mostly, but as this applies to the contents of the inputargument, this could be anything, even strings (which can contain ';' themselves). This however rarely happens.
You can check an attribute's type using either an actual MxObject you already have or by retrieving the meta data using the entity name. Both of these have functions for the important ones, isDate, isNumber, isEnum. Besides these you can usually consider them as strings for the scope of your widget.