What these guys said is the truth for the most part.
In general 5 lug = 3,500# and will have 14" or 15" wheels
6 lug = 5,200# or 6,000# and will have 15" wheels
8 lug = 7,000# will have 16" wheels
Anything with 13" wheels can be 4 or 5 lug and 2,000# or less axles. Smaller wheels, like on a jet ski trailer or log splitter, are commonly 4 or 5 lug and 1,200# axles.
Like mentioned tires are usually the limiting factor.
Close pictures will tell me a lot. I am a boat trailer dealer and while I have not seen it all I deal with plenty of stuff.
Chris