I had a similar issue with a big Assembly (it was the PTC edc world car Assembly.)
The size of this Assembly and Components is around 500 Mb.
It was taking some time to display the geometry in 3D in Thingworx.
So, at first, in Creo Parametric, I created a Shrinkwrap of this Assembly and export it as a pvz file.
It is not needed to export and load in memory, in Thingworx Studio, in the Experience, 3D geoemetries who are not visible.
At second, I switched on the Run CAD optimizer checkbox and select the low Level Of Detail.
At third, we can have a log into the log file.
It can be useful to have more details