Sketchup free runs in your browser. its performances won’t depend only of your gear, but also of your bandwidth, stability of your connexion, running speed of the servers and their availability (these last few days there has been some crashes). Also, it’s like an emulator, I mean, SU works in addition / inside the limitation of your browser.
So yeah, it’s a free version, and its performance is limited, regardless of your hardware.
The pro version will be able to use your hardware better.
be warned though, SU (like other 3d softwares) will only use one core of your processor (single thread process), and will barely touch your graphics card. so the difference between a 1000$ and a 4000$ machine might not be THAT visible. especially considering the price of graphics cards and processors.
EDIT : here is a thread that explains better than I do why high end gear might not result into super massive boost compared to medium-end.
But don’t trust my word on this, try it. You have access to the free trial (30 days)