one axle vs. two axles on short TT (20')

I didn't know anything about rubber torsion axles until now. I thought all trailers had leaf springs. I found some pictures of and can tell them apart now.

I looked at a couple of websites for trailers and it doesn't look like they discuss what type of axle or the weight specs of the axle the trailer has. How do you get this from the web?

Thanks again for all the info.