Well, it depends. If you do the set it and forget it method for carbonation, then no, the carbonating pressure and dispense are the same. There are several carbonation tables in the Kegging FAQs and several calculators if you google as well. All you need to do is set it to the desired pressure for your level of carbonation, leave it for a week or so, and it'll be carbonated.
If you were to turn down your serving pressure, the pressure in the keg would lower and the carbonation level of the beer would drop.
There are other methods of carbonating, setting to 30PSI and shaking the keg for a few min, or setting at 30PSI and letting it sit for 48 hours to carbonate, but the results can be inconsistent.