You need to balance your lines so you can carbonate and push the beer out at a reasonable speed.
This is google randomness on the subject,
http://www.brewersfriend.com/2009/07/18/getting-a-good-pour-kegged-beer-co2-line-length-and-pressure/
There's a spreadsheet linked on here somewhere on balancing your system.
You can strike for a compromise carbonation level between two kegs of different styles, so the whole setup will balance at the same level.
This is probably the most straightforward way to start with.
Otherwise, you could carbonate Keg #1, say at 2 volumes, disconnect it from the gas. Then connect and carbonate Keg #2 at a higher level, say 3.7 volumes and drink it.
Disconnect #2 and connect #1, drink it. etc.. = 2 kegs at different carb levels. Always isolated from each other so they don't balance to the same carbonation level.
Or dual output reg,, or...
It does seem like with just two kegs dual output reg is possibly overkill, just my (badly expressed) 2c but then I have 5 kegs and a dual output reg so...