I have possibility to get auxiliary models as STEP or JT format, I tried to search what are the major differences between these but didn't found clear answer. Anyone have experience which is better? I have always used the STEP-files, and now noticed that SW2018 can open JT files also.
i don't have very much experience with importing JT to SWX since it is possible with the actual SP3.
But maybe JT will also transfer meta data information to SWX; this could be an important feature... (but should be verified).
So my advice for you is: Try both out and compare quality, speed, and additional data (metas) and the decide. Very often it's not only the import on your side, but also the export on the other. So there is nothing better than a real-live-test!