How are you importing the Inventor parts? As .ipt files or as Step, iges or something else.
Do you have inventor on the same system as the one that has SolidWorks?
If not, do you have Inventor View on the SolidWorks computer?
I have only used Inventor files from Inventor 7, 08 and 12 and converted them to SWX 2014 or 2015 so I am not sure if newer versions of either one (or each) makes it any better - but I have never seen anything to indicate that it has.
I have never been able to import the i-properties as this is in the meta-data and when Solidworks imports the part it is as a dumb solid that does not seem to contain the meta data - or at least it is not imported)
If you have Inventor (or Inventor View) on the same system it seems to use a conversion method that I think (not for sure) is part of Inventor that does a much better job of converting an .ipt into a SWX part than you will get if you use SWX Feature Works to convert the part.
I have also only been able to import a sheet metal part as a part - no sheet metal features (bend lines, flat pattern...) got imported.
I do have a professional license of Autodesk Inventor 2017 and Solidworks 2016 installed on my system.
There is feature in SW that recognizes and lets a sheet metal part that gets imported as solid to be converted back to sheet metal. Biggest issue is while converting assemblies it looses reference to constraints which needs to be redone and parts sketches looses reference to origin.
Whenever you import a part - and convert it - you will loose the relations and you will have to recreate the relations.
Starting with SWX 2017 there are more options to use a Non Native part (like an Inventor part) in your assemblies without converting them.
They become dumb solids (not editable) but are usable without converting.
But with 2016 and earlier, you need to convert.