Looking for info on Hub caps. I searched around and didn't find much.

I have the Cleveland 6" wheels and the Grove 1.25" axle. I am a little confused on what hub caps I need. I have seen the pie pan caps with the 3 holes on the perimeter and it looks like they line up with the 3 holes on my rims. Then I have see some that have a hole in the middle on the hub cap? The end of the axle is threaded so do the hubcaps mount here and are stationary?

Looking for some enlightenment......

On a side note.....Do most not even run with hubcaps? Seems like there needs to be a way to check air pressure without removing the hub cap?

Thanks
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