What is the difference between an EPL and a profile?
An EPL controls how ink is applied to a media by the proofer.
It controls channel limits, meaning how much of each individual ink is actually used of the total ink the proofer can supply (i.e., only use 90% of Cyan, 85% of Magenta, etc.) and it also controls total ink limit - how much ink in combination is allowed? For example: if CMYK at 100% each is a total of 400%, the EPL might only allow 300% ink in total to be applied.
A good EPL will allow the proofer to put down enough ink to get good color, but not enough that the proofs do not dry, there is no puddling or smearing, etc.
A profile defines the color space of a proofer. This determines what colors are within gamut (i.e., directly reproducible) versus which colors must be interpolated to be reproduced. The profile is the basis with which one color space is translated to another, for example, press to proofer.
The profile is dependent upon the EPL it is associated with. It is not a good practice to use a profile with an unassociated EPL. The results will be unpredictable.