Rope chains are typically used to wear pendants, as they are fairly strong in comparison to other types of chains, such as flat chains. If you are planning to wear a heavy pendant, you will need a thicker chain to wear it. One caveat to be aware of, however, is that unlike link chains, rope chains are not as easily repaired.
When purchasing a rope chain, you should twist the rope a little bit. The point is not to see how strong you are, but to determine how well the chain is constructed. You will be able to twist loosely assembled chains to a greater degree. If you are planning to wear the chain by itself, this is not an issue--you may even prefer a loosely woven rope chain