You don't need to use that special tensioner. It's probably there for whatever specific purpose the machine was set up for. I could see it being helpfull if you are sewing long seams at a very high rate of speed, as then the thread can really get whipping around coming off the thread spool. It's a big reason the machine has holes for threading instead of "self threading" openings. That way the thread can never pop out on you. My long arm is the same way.
My Juki 8700 does not have anything other than normal thread guides on top, and it sews fine that way. I use 50 wt thread for the most part.