I came from an Altium background and when I started my own business I needed something more affordable. I checked out about a dozen PCB design programs before settling on CircuitStudio. I really liked the features of Altium and CS seemed to be the closest. It does lack a few things that are available in Altium but the structure is there.
Regarding the free trial or purchasing, I have never had a problem with registering my information. I wouldn't know where to start. It's been so long since I first set it up.
With regards to Solidworks, if you can export step files from Solidworks, you can import 3D objects into CS. I use step files for all of my parts. Not only does it allow me to verify fitment of the parts, I am also able to customize all of my parts. If you are trying to import your PCB into Solidworks, I have never tried that. I'm certain that it wouldn't be too difficult as CS does provide a 3D model export feature.