FreeCAD, in theory, should be pretty similar in interface terms and workflow to most of the common industrial (usually autodesk) products, so if you learn it you'd be well prepared for them if you ever find yourself working for someone who uses those. You should hopefully be able to model any geometric form, however complex, that you want using it. But if you want to start making things LOOK nice (you said you were interested in architectural rendering) for still images or video you'll want to learn blender (you can probably convert finished freeCAD models and then import them to blender to animate and render them there.
Sketchup, by the way, is limited but can still model any geometric shape you want (though it's hard for really complex forms like screw threads and worm gears), it'll just need you to think about the shape in different ways until you work out how to construct it line by line. For someone like me with years of experience I find it a nice tool but still turn to other software t make certain kinds of shape that I then import to sketchup, and then export from sketchup to blender for final finishing and rendering. Sketchup thesedays is owned by a company called trimble, google sold it to them in about 2012, but I still use a really old sketchup version so the version I still use is a google product. Thankfully it does not need any cloud or other internet connected elements, you can run it entirely from your local machine, no need to rely on any google (or trimble) servers half a world of slow or failing connections away.
Edited by rp88, 24 March 2018 - 04:32 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB