Ashlar-Vellum has a suite of Mac-native CAD applications that are very good. Good enough for
SpaceShipOne, anyway.
I've used their Graphite 3D wireframe and its predecessors on Macs for eons. Ashlar was a pioneer in parametric modeling and design, but never was able to match Autodesk's marketing clout.
That said, I think Inventor is a better solution if you have the machine to run it. You didn't say what model laptop you got - if it's Intel, it should run some version of Inventor, though just like with a PC, you need a top spec machine to run the latest version well.