Nekmo can't really be tuned because of the randomness of his kit.  Anyone with a consistent effect can be tuned.  

As for Speed Buff vs TM it's kind of two sides to the same coin.  Speed buffs generally require either 2 Speed buff champs or 1 and an extender to maintain it full time.  TM boosters can do it alone but really you need Deacon or Seeker ( Inbuilt extra turn mechanics act as if the TM boost is on a 2 turn CD ) to be most effective.