FreeCAD is definitely worth looking into. I installed it once, but didn't get to mess with it much. Maybe I'll try it out again at some point, but who knows what the future holds in terms of support.
I've been using TurboCAD since 2001 and began using the 3D capabilities of the Pro version five years ago. It's still my primary program for 2D and 3D, and I've used it extensively for complex scale parts uploaded to Shapeways (see link below signature). Buying the Pro and Platinum versions outright would be expensive, but fortunately, older versions can be found for much cheaper (for example,
https://www.cadandgraphics.com/ has TurboCAD 19 Pro for $229...sometimes you can find deals on Ebay). And those older versions can be upgraded to the latest version at a discount, as IMSI/Design's licensing rules don't seem to be as strict as most. I don't recommend the Deluxe program for 3D work, since you really need the ACIS modeling capabilities of Pro TurboCAD (old Pro is still better than new Deluxe for 3D work); however, even Deluxe users can upgrade to Pro or Platinum at a discount ($700-$800 currently). My only real gripe with the program is a switch to a default dark theme as of version 19 which I think is done poorly (I switch mine to a lighter one, but sometimes there are tool icon bugs with the lighter theme).
I tried the 123D program once a couple of years ago (based on the non-parametric Inventor Fusion). The main problem was a serious limitation of resolution when outputting STL files; you really should use something that's going to give you options to vary the resolution of the tessellated surface.
On a related note, I put together a page detailing my workflow in fixing STL files prior to uploading to Shapeways, using the free program netfabb Studio Basic:
https://meatballrocketry.com/netfabb-fix-stl/ ...
Good luck on your move into 3D.