Monitoring the channels in an emergency for anything “official” might be very iffy. GMRS repeater users (and their hardware) may actually be down during a natural disaster.
Here, the use of consumer grade radios would be to help your family and neighbors, so range shouldn’t be a huge issue.
However, understand that HEIGHT and lack of obstacles will allow you to get a lot of range. I have done many many miles only when there is height and clear line of sight - AND both parties are actually holding their radios nearly perfectly upright! Holding the radios in a sloppy fashion where the antennas are not both vertical (held like a cellphone off at an angle) can really attenuate the link. (cross polarization)
The general rule of thumb is that if both parties have radios at 6 feet high (radio held above your head), the signal (with no obstacles intervening) will go about 3 miles before the curvature of the earth gets in the way. So 6 mile links are possible near ground level, but put a building in between - range drops dramatically. Height beats increasing power any day. Still, it all depends on the environment.
Also to be considered is that with inexpensive consumer radios, the receiver is not the greatest - your transmitted signal may actually be reaching your destination, but the receiver in the frs radio is easily overloaded by nearby transmitters, resulting in images, intermod, desense and other nastiness. This is particulary true of city dwellers in tall buildings on the high floors.
The saving grace for these inexpensive radios is that they can run off non-proprietary AA / AAA, either alkaline single use, or rechargeables - my fav are Sanyo/Panasonic Eneloops. A $5000 radio is worthless if you can’t recharge it. One of the reasons I favor Cobra radios is that they will also charge your own non-proprietary batteries via a modern micro-usb port - albeit VERY slowly. I have a USB 10ah Anker lithium battery that I charge via solar, and then of course can charge the Cobra’s with. I wish the Motorola bubble-packs did that, but unfortunately you are stuck with their own batteries for recharging. Part of my “go bag” especially if I’m forced to evacuate to a shelter.
So while consumer grade radios aren’t the best radios in town, when the chips are down it is better to have something than nothing. Much like having $10k of camera equipment left at home when all you have with you is your cellphone camera. At least THAT is with you!
Update: I have basically gone back to Motorola despite the inability to charge NON-oem batteries from usb. Everyone has their fav I suppose…