To try and answer the original question...
Yeasts are fickle beasts. The "right" temp for any yeast is the temp that delivers the flavor profile you want from the yeast. You can hold a strain at the low end of its temp range, and if you used the exact same ingredients/procedure but changed the temp to the high end of the range on your next batch... you might get a very different end product. Each strain of yeast has a unique behavior profile across temp ranges. Generally speaking, towards the higher end of a given strain's temp range, you will see more phenolic compounds and esters (have to be cautious of chlorophenols and fusel alcohols though), lower temp will not produce as many. So much depends on the yeast strain....
After that you have to get into adequacy of aeration, nutrient levels, pH, sugar profile of the must or wort, pitching rates, and a couple of other variables that can alter yeast behavior.
For a sweet mead what I like to do is start a little warm (pitch at the high end of my yeast's temp range), hold it there for about 12 hours after lag phase ends, and then back it down a degree every 6 hours until it I get it do 68-70. I like wyeast 4783 for a sweet mead, so I let it start at 75 and walk it slowly back to 68. That is close to the top end of its temp range and usually imparts some subtle spicy ester notes along with fruity sweet profile. Did two 5gallon batches with this yeast (and that temp schedule in primary) and some local orange blossom honey last year, my family has literally stolen every bottle!
If I use that same yeast and held the temp at 60 for the entire primary, I would expect a good sweet mead at the end, but the flavor profile would probably change.