When you change the Electro Osmotic Flow (EOF) of your CZE method, the following changes can be expected.

Joule Heating: Reducing or lowering the EOF will reduce the amount of Joule Heating in your capillary.
Migration Time: Changes in EOF will directly effect the migration times of all of your analytes. The changes are not always proportional and this may affect your peak shapes and peak areas.
Resolution: When EOF is reduced or eliminated Resolution can be enhanced.