Goldtrap,
Since none of these plants have been registered as cultivars, and no one has measured and defined the characteristics, the only way you can really tell is to try different seed from different growers. Then, the thinnest lamina form would be "thin leaf", the next widest form would be "typical" and the widest form "wide leaf" (at least in your collection). It is all opinion until something definite gets set in stone via publication. It is always possible that another grower has a thinner leafed clone than your "thin leaf", and inevitably this hypothetical grower would not agree that your plant was "thin leaf" since his would be thinner! This is why we need to register and define these forms. Until this is done, all speculation regarding unpublished measurements ("Large" "Typical" "Thin" "Wide" "Giant" ) are just that: speculation and opinion.
In botanical terms, there is only Drosera capensis, which is a variable species. Adding anything after the binomial (unless it is published as a cultivar) is therefore largely useless for purposes of communication.