Not a dumb question yet it is a complicated one, in a way.
Micing a speaker in itself can create seemingly limitless variations. To mic a speaker you need a power amp. This power amp may be flat response or many times not flat response. This power amp response will effect the IR. You can subtract the power amp coloration from the IR to make it just the speaker, microphone and room. Microphone position and the room they are in being the two parts that you are left with for variations.
The Kemper shoots the profile (including the speaker etc.) of the whole setup at once for a studio profile. In this situations the cab driver on the Kemper separates the amp and cabinet based on a formula. Not a bad one either.
A direct amp profile is of the pre and power section of the amp with the impedance interaction of the power amp speaker included. You can then create a studio profile of this exact setup and merge it with the DA profile to get a separated cabinet.
Without knowing what method exactly is used by any author it is tough to say what the differences are.
The Kemper can substitute a cab from any method for the other but it may or may not be authentic.
In the end, really all that matters is what works for you.
There are some free IRs from Celestion in the Kemper factory content. I believe these are IRs converted over to Kemper cabs.
Hey guys. I'm fairly new with the Kemper and a little confused about cabinet IRs from Celestion. What's the difference between buying the Vintage 30 4X12 Closed Cabinet IR from Celestion verses copying the exact same cabinet from a TopJimi profile I have and pasting into another profile?
The cabinet might be the same, however the microphone used by the person who created the profile / IR and its position in front of the speaker may be different, and that will have a big influence on the sound. The mic preamp(s) and other gear that was used to capture the IR / profile may be different and can also influence the sound.
while all components like the speaker itself (just because it is the same speaker model doesn't mean it sounds exactly the same, plus a well used speaker will sound very differently from a new one) microphone etc. do matter, the biggest factor is mic positioning.
Even an experienced engineer, given the very same components can't really re-create a sound recorded previously if the mic was moved. (hello drunken drummer stumbling through the recording booth at night) 
In short,
just with one mic and one speaker in one cabinet you can create dozens upon dozens of unique sounding Profiles.
This is the beauty of profiling as opposed to the somewhat more generic IR approach.
