I played with a genuine erector set as a kid. I didn't find it to be particularly engaging (I spent a lot more time with Construx), so my experience was short lived, but I did play long enough to remember some details. I think the fasteners, the wrench and the metal struts themselves were probably about on par with this cheap one you bought. The wheels though, for some reason I think mine were made of wood and they definitely weren't off center. They were given to us when our great grandfather passed, so I think they were quite old.
I remember Construx. I had a car kit from that line as a kid. I still have some of the pieces in an official yellow Construx case I acquired some lime later. It's all in my garage sale pile now.
I always thought Erector would be ideal for train set trestles, but I never had a proper train set. I did have a LEGO train set though, and that was awesome.