1/8 = BMX chain.. regular chain
3/32 = road chain...

Doesnt matter basically if u have 1/8 or 3/32 because almost all the people is putting trac/bmx chains on their bikes (some people dont, but bikes bought in a lbs have 1/8 chains). So anything u get it will work because obviously the chan is wider and the 3/32 teeth fits anyways.

Cogs usually tight when u are pedaling so is quite easy to know where it tights and were to lose... the only problem are the lock rings, some companies do the lockring thread to tight or lose at the same clock turn as the cog (stupid idea) but well.... i have no clue about the iro hubs but apparently are jusy like any other fixed wheel? did u figure it out if u have a lockring on?

If u want to make a cheapo tool to "unscrew" cogs grab a set of PLIERS VISE GRIP STYLE ...and a piece of 1/8 chain long enough to give 2 turns around the cog. Now I think u figure it out... apply torque obviously in the way to unscrew the cog OK? Ive seen idiots do it at the otherr way and screiwng up the thread... well i saw a guy putting the pedals at the opposite direction, the worse part is that he made it in both pedals, DAMMM!!!!!!!!. I think U can figure it out. All make too much sense...

Cya around...