You can't tell the difference just by the booking class, it all depends on the individual fare rules and these vary by point of sale, by type (published / negotiated corporate fare).

Ex Europe for example you can buy a ZNCXXX, a ZRCXXX or a ZFFXXX fare to destinations in North America. All three fall within the Executive First (lowest) category, they all book into Z class but the ZNC fare is non-cancelable, the ZRC fare is cancelable for a fee and the ZFF fare is fully flexible. So you can have different sets of rules even within just one letter, therefore you can't generally say a fare in booking class H has these set of rules and M has these set of rules - as in many cases in life, it all depends...