My actual electronics "knowledge" is arm-wavy at best - I have played with radios a bit and I have a "no-code tech" ham license.

My now-ancient Radio Shack HTX-202 2M handy-talky has a power level switch, which locks the power output down to 1W, with the express purpose of conserving battery power when the extra range is not needed.

When this switch is out, then the (attempted) output power level is automatically set according to the input voltage supplied.
So if running off the stock ni-cad battery pack, it might put out 1W to 3 or 4 W depending on the charge state.
It will also run straight off of the 14V power available in a running vehicle, and put out 7W RF at the maximum.
Add to this a real antenna (at 2M a rubber duck is not really an antenna) and you have a useful mobile rig.
It is really a marvel of flexibility.

I don't think the Kenwood GMRS radio will have this sophistication, since it requires a battery eliminator to run at "12V".
I suspect the battery eliminator will have some noise suppression components in it as well, not just a voltage regulator.

You might find the information here interesting:
http://ba-marc.org/writeups/gmrs-frs-freq.htm

Note that the FRS and GMRS frequencies overlap.
So the requirement for licensing really depends on the power output and the question of whether the equipment has been modified since it was manufactured.

FRS has no license requirement but you are limited to .5W and forbidden to modify the radio in any way, including using a better antenna.
The strictly FRS radios you find in Wal-Mart have a non-removable rubber ducky antenna.
With GMRS the upper limit is 50W (which is a lot but not ridiculous) and you are free to modify the equipment, use better antennas, etc.

Notice that GMRS users are expected to give their call sign (issued by the FCC) when transmitting (every 10 minutes) even if they are speaking to an FRS user on an FRS channel. Why do you think this is a "requirement" ? - It is so that if anything is discovered wrong with your transmission (which could be anything from a technical issue or could be cussing on the air or propagandizing for some foreign power...) then the FCC would theoretically be able to track you and your radio down and get the problem corrected. Their solution might be sending you a letter or in the extreme might be revocation of license and confiscation of equipment. In theory.

The main thing the FCC is concerned with is that everyone is allowed to use the airwaves and that no one interfere with anyone else trying to use the airwaves. So, with an unmodified 2W GMRS radio it is extremely unlikely that it will interfere with anyone else. So the only way in which you would be in violation would be in not announcing your call sign. I can also assure you that the FCC does not have an army of agents (unless you count us hams) going around looking for GMRS violators. There's no budget for that.

FRS is what CB was supposed to be. If you listen to the CB band nowadays you'll realize that it is completely out of control. There are truck drivers running 1500W CB transmitters, no license, completely made up "handles" instead of callsigns, no way to track them or enforce any rules.

I guess in other words, I would encourage you to buy the GMRS license and to conform to the FCC rules just as an act of patriotism, in recognition of the freedom we have to use radio this way. Many people around the world do not have these priviledges. But I'm also saying that there is no way any of us are going to know whether you did or not.