Most OEM wheels are HUBcentric, which means the hole in the hub is machined to precisely fit over the hub projection on the axle spindle. So, the weight is borne by the hub and the studs basically just hold the wheel to the hub (as well as prevent the wheel from rotating independent of the hub).
Many aftermarket wheels are LUGcentric, which means holes through which the lug studs come through the wheels have a "cone shape" machined into them, and you use a matchingly shaped lug nut. This centers the wheel on the studs, and now the lug studs themselves carry the weight.
With lugcentric, it doesn't matter if the opening is a half inch larger than the hub on the axle; the lug studs take all the load. But if you're setup is for hubcentric, then you have to have a tight fit.
Personally, I think hubcentric is a better design, but I have used the others with no problems as well.
Best of luck!