So, I was in the exact same boat as you. I looked around online, found some brands I liked the look of, and went to my LBS to order them. The guys at the LBS told me they thought that if I pulled the axle out of alignment that the nuts were too loose, and that the fix was just to keep them tight. They said that if I had a chain tug on there, it would probably just break, and that those things are mostly just for tensioning the chain in the first place. I can tension the chain fine, but it does slip every so often.

So, I'm just trying to recheck the torque on the axle nuts every week or two using a ~12" flare wrench. I also pulled the wheel and made sure any paint left in the dropout where the axle nut clamps was rubbed away. I carry a small adjustable wrench in my backpack too. Maybe the guys at the LBS are wrong, but my impression of those guys is that they both know what they're talking about and are entirely honest (the advice that they gave me did cost them a sale). So- that's not what you asked, but I thought it might help.

In any case, you definitely don't need two chaintugs.