When to use maxspeed:type, zone:maxspeed or source:maxspeed?

Sorry, I don’t get your point. Yes, there is as I already wrote the difference that I can’t use zone:maxspeed with value sign but what can I do with zone:maxspeed what I can’t do with maxspeed:type or source:maxspeed? There are differences in usage (counts), but the wiki pages describes since their creation the same (with the exception of “sign”)