Neat idea, I'm always in favor of saving a few bucks.
A quick look at the chemistry says there's really not much difference in heat produced, or oxygen requirements on a pound per pound basis. The difference is entirely in the pressure, at room temp isoButane is ~45% higher than n-Butane. So you're getting considerably more gas out of your lighter using the higher pressure fuel, confirming your guess that it runs rich, and why moving the lighter around helps combustion. It also suggests you'll be using more fuel (unless you can adjust your lighter) per light. Since you're in a rich environment, I'd guess using these fuels will actually have lower combustion efficiency than n-Butane.
Propane has an even higher pressure, so I'd guess this 'running rich' problem would be more prevalent in the blends with higher amounts of propane.
On that same note, the blends with n-Butane in the mix should have a lower pressure, and lower oxygen requirement (though still higher than neat n-Butane). If the reason for switching to one of these camp fuel gases over the 23x distilled cigar lighter gas is purely economical, why not try these blends? Assuming the fuel is clean and extreme cold weather performance isn't your goal, they may actually work better than the 80/20 blends. Especially in a lower oxygen environment.
On the other hand, if you can adjust the flame down, you may get better performance with lower fuel usage (comparable to 'regular' n-Butane).
But that's a lot of guessing on my part and my coffee hasn't kicked in yet, so I could be wrong. I might need to get a few Ronsons and a couple cans of fuel and have some fun with this
Edit: Just another thought, I wonder if the higher pressure might increase reliability in windy environments, i.e. make the flame more 'wind proof'?