MEMCOPY works with strings of same max sizes, e.g. SS0 to SS5. But it does NOT work with SS0 to SL0 since SL's max length (256) is different than SS (64).
STRCOPY takes any combination of string maxlengths, and when copying shorter max lengths to longer, it just works. And when copying longer lengths to shorter max lengths, it truncates the longer string to the destination's max length so that memory is not overwritten.